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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]

This paper is focused on the detailed lithostratigraphic facies characterisation of the paleo-environments of the uppermost Silurian through Lower Devonian Winduck Interval strata from the Bancannia South 1, Pondie Range 1 and Booligal Creek 1 and 2 wells, across the central Darling Basin of western New South Wales. Based on data from both wireline logs and drill cores and cuttings, an interpretation of paleo-environments and evolution of the depositional facies is presented. Our approach involves two key interpretations. The first outcome was the delineation of the Winduck Interval section (maximum observed thickness of approximately 1475 m) and formal subdivision into lower and upper Winduck Intervals, based on well data from the central Bancannia Trough, southern Pondie Range Sub-basin and northwestern flank of the Blantyre Sub-basin. The second outcome is based on the internal lithostratigraphy of the Winduck Interval represented by 11 sedimentary lithofacies organised into three lithofacies associations (LFAs). LFA-X1 is interpreted as distributary-channel sandstone complex deposits, LFA-X2 is interpreted as distributary mouth bar with small-scale braided delta plain complex deposits and LFA-X3 is interpreted as tidal channel sands with proximal delta front complex deposits. Subsurface lithostratigraphic facies analysis relationships and depositional environments of the Winduck Interval section have implications for evaluating the hydrocarbon potential and may assist future exploration efforts in the central Darling Basin, especially the Bancannia Trough and Pondie Range Sub-basin. A detailed lithostratigraphic facies characterisation of the paleo-environments of the uppermost Silurian–Lower Devonian Winduck Interval strata in the central Darling Basin is presented. Evaluation and interpretation of the Winduck Interval section in study area was subdivided into two informal stratigraphic units, a lower Winduck Interval and an upper Winduck Interval. Eleven distinct sedimentary lithofacies codes (LFs), which have been recognised in the internal lithostratigraphy of the Winduck Interval from the Bancannia South 1, Pondie Range 1 and Booligal Creek 1 and 2 wells, have been grouped into three lithofacies associations (LFAs). Lithostratigraphic facies analysis relationships and depositional environments of the Winduck Interval section has implications for evaluating the hydrocarbon potential and may assist future exploration in the Bancannia Trough and Pondie Range Sub-basin. [ABSTRACT FROM AUTHOR]

For the past 200 years, there have been numerous investigations and much speculation concerning the formation of the dramatic valleys of the Blue Mountains of NSW. In this paper, further evidence for the uplift and erosional history of the Blue Mountains is obtained from longitudinal river profiles, detailed mapping of the Rickabys Creek Gravel on the Lapstone Structural Complex and consideration of the topographical position of Miocene basalts. Knickpoints on the main rivers flowing east from the Great Dividing Range are identified and interpreted to be due to uplift events linked to the northward movement of the Australian continent over mantle inhomogeneities. At the Lapstone Structural Complex on the eastern range front, the occurrence of the Rickabys Creek Gravel and the nature of the over-steepened reaches on the rivers and streams crossing the Complex, suggest a more recent ongoing phase of uplift and antecedent river erosion. The Miocene basalts provide evidence of this landscape 20–15 Ma. Their locations with respect to the current rivers and ridges are interpreted to show additional evidence for recent uplift that has resulted in the formation of the Lapstone Structural Complex. It is suggested that this uplift commenced 10–5 Ma when the contemporary compressive stress field was established. Longitudinal profiles for major rivers in the Blue Mountains are consistent with a model of initial Cretaceous uplift followed by further Cenozoic uplift associated with dynamic topography. Mapping of Rickabys Creek Gravel within the Lapstone Structural Complex suggests the presence of antecedent rivers. Within the Lapstone Structural Complex, stream profiles, gravels and nearby outcrops of Miocene basalts are interpreted to indicate a third phase of uplift, possibly since 10 Ma. [ABSTRACT FROM AUTHOR]

The Cliefden Caves area in central-western New South Wales includes the scientifically most important and irreplaceable examples of fossiliferous Ordovician rocks in the State. Exposures of the stratigraphically lower parts of the Cliefden Caves Limestone Subgroup on the aptly named Fossil Hill are world-famous among paleontologists and internationally significant for preserving the earliest in situ shell beds documented in the literature. They also contain some of the oldest known rugose corals, and an exceptional example of one of the oldest coralline biostromes, as well as many examples of invertebrate fossils and cyanobacterial mat structures that either are unique to this locality or were first described from here. Other stratigraphic levels throughout the total 363 m-thick Cliefden Caves Limestone Subgroup are similarly endowed with highly significant fossils, such as a globally unique in situ shell bank with rare examples of the trimerellide brachiopod Belubula spectacula, a wealth of shelly fossils and trilobites on Dunhill Bluff (adjacent to Fossil Hill to the east), and the appropriately named Trilobite Hill. Less well known to the general public, but of international importance to paleontologists, is the unique deep-water sponge fauna of the overlying Malongulli Formation that occurs at several levels in limestone lenses within this unit. Fossils from the Cliefden Caves Limestone Subgroup and the Malongulli Formation have been documented in more than 60 scientific papers and monographs since paleontological investigations into the site were first published in 1895. Despite concerted scientific endeavour in the region over the past 50 years, much more study needs to be done to fully document the paleontological riches of the Cliefden Caves area. These sites are interpreted as the remains of a tropical island, fringed by limestone and flanked by deep-water environments in which the Malongulli Formation was deposited. Preservation of such islands is exceptionally rare in the geological record. It is therefore vital for the area to remain accessible to scientific researchers to continue their studies. Flooding of the Belubula Valley by a proposed dam downstream from the Cliefden Caves area would hinder future research work on this unique geoheritage resource. Fortunately, a successful public campaign has led to listing of the site on the State Heritage Register that will provide essential protection of the caves from inundation while ensuring continued access to researchers. [ABSTRACT FROM AUTHOR]

Late Holocene environmental changes were examined in Dee Why Lagoon, New South Wales, based on the sedimentological, geochemical and geochronological analysis of six cores collected from the fluvial delta and lagoon basin. The lagoon formed about 7300–7200 cal yr BP, following the post-glacial marine transgression and establishment of a sand barrier. Infilling of the lagoon occurred at a rate of 0.09–0.15 mm/yr until about 3300–3200 cal yr BP, when the barrier closed, resulting in mostly freshwater conditions, as evidenced by a change from pyrite-rich units to sediment containing little sulfur and a lack of foraminifera. Sedimentation rates increased to 0.23 then 0.43 mm/yr until about 100 years ago. Post-European land clearance led to an increase in sedimentation rates to 1.0–1.3 mm/yr on the fluvial delta, which are lower than those from other wave-dominated estuaries in New South Wales as well as those estimated by previous studies in Dee Why Lagoon. Our study shows that the fluvial delta started forming much earlier than originally thought, based on results of radiometric dating, and confirmed using sedimentological and geochemical data, as well as a critical examination of historic aerial photographs. Human impact has resulted in an increase in heavy metal (Cu, Pb, Zn) and metalloid (As) concentrations in the recent sediment, most likely attributed to stormwater discharge. Pb and As concentrations are above the ANZECC high sediment quality guideline values at the site closest to the stormwater outlet, with As-based pesticides one of the possible sources. Using the mean enrichment quotient, which is based on normalised Cu, Pb and Zn concentrations over their normalised background concentrations, we show that the surface sediments in Dee Why Lagoon are severely enriched, reflecting the recent anthropogenic impact that has also led to an increase in sedimentation rates. [ABSTRACT FROM AUTHOR]

The southern Cobar Superbasin includes the Mount Hope, Cobar and Rast troughs and adjacent Winduck, Mouramba and Kopyje shelves. These stratotectonic units host a range of mineral systems within deformed upper Silurian to Lower Devonian rocks. Despite the metallogenic importance of the terrane the regional metamorphic- and alteration-related mineral assemblages have not been systematically described until now. Here, we present a study using the HyLogger™ spectral scanner to systematically map changes in both background and alteration-related mineralogy for 14 mineral systems across the Nymagee area. The study found that, with the exception of the late diagenetic zone assemblages associated with the Winduck Shelf, the mineral assemblages for zones away from mineralisation are consistent with uniform sub- to lowest-greenschist facies metamorphic conditions, with no evidence for a regional, thermal field gradient across the basin. By contrast, proximal to mineralisation, there are significant changes in alteration-related mineral abundances and species reflecting elevated fluid temperatures. For several zones, including Browns Reef, Great Central, Hera, May Day, Nymagee and Shuttleton, there is a systematic change in chlorite composition from Fe- and/or Fe–Mg-chlorites to more Mg-rich varieties towards mineralisation. In addition, talc was noted for May Day, Mineral Hill and Shuttleton. The change in chlorite composition suggests that these ore-forming fluids were undersaturated with respect to iron. Furthermore, although present in discrete zones, carbonate alteration is not a dominant alteration type. However, at Manuka and Blue Mountain, the mineralisation is associated with carbonate-rich (calcite, ankerite, dolomite) units that have been dolomitised (Mg alteration) but not all dolomite-rich zones are mineralised. For Mineral Hill, there are systematic changes to mineral species/chemistry with observed data consistent with Parkers Hill being proximal to the centre of a mineralising system. The G and H Lode area (Southern Ore Zone) is slightly more distal whereas the Pearse deposit may represent a zone more distal again. [ABSTRACT FROM PUBLISHER]

The Ordovician Turquoise Bluff Slate in northeastern Tasmania is a 2 km-thick sequence of deep-marine siliceous black slates. It is dominated by meta-siltstones with bimodal grainsize distributions typical of turbidite TE-1 and TE-2 facies. The slates have high SiO2 indicating they are hemipelagites. The high Ba and V indicate they were deposited in an anoxic environment associated with high oceanic productivity. All these features are common in muddy turbidites. U-Th-Pb dating of detrital monazite and authigenic xenotime in the slates supports previous evidence that the dominant cleavage, in this unit, formed during the Benambran Orogeny. The whole-rock composition of the slates is similar to black slates in the Adaminaby Group, NSW. A review of Paleozoic whole-rock compositions from the Lachlan Orogen confirms they all have trace element contents similar to average Australian shale. However, there are subtle differences in composition. The Turquoise Bluff Slate and other Mathinna Supergroup rocks from the Eastern Tasmania Terrane have higher average Cr content than similar age turbidites from Victoria and NSW. This probably reflects a small contribution from Tasmania Cambrian ultramafic rocks in the provenance. If this were correct, northeastern Tasmania was closer to western Tasmania in the Paleozoic than other provinces of the Lachlan Orogen, southeastern Australia. Other subtle features of the whole-rock composition of Paleozoic sedimentary rocks from the Lachlan Orogen indicate it may be possible to recognise provincial variations in composition that will provide new constraints on tectonic models of southeastern Australia. [ABSTRACT FROM AUTHOR]

This study documents Middle to Late Ordovician conodont faunas primarily from the Billabong Creek Formation exposed in the Gunningbland area located west of Parkes and northwest of Forbes in central New South Wales. Forty-four identifiable conodont species recovered from 105 limestone samples in this area form the basis of the most complete biostratigraphic succession in shallow-water facies known through this interval from Australia. Four conodont biozones are recognised, extending from the middle Darriwilian Histiodella holodentata–Eoplacognathus pseudoplanus and Eoplacognathus suecicus biozones, through the upper Darriwilian Pygodus serra Biozone, to the Pygodus anserinus Biozone spanning the uppermost Darriwilian to basal Sandbian interval. A lower to middle Sandbian carbonate gap coincides with an unzoned interval, followed by the successively younger Belodina compressa, Phragmodus undatus and Taoqupognathus blandus conodont biozones in the upper Sandbian to lower Katian. The T. blandus Biozone directly correlates with the detailed conodont biozonation established in Katian limestones of the Molong Volcanic Belt further east. These age determinations provide much improved precision for correlation within Phases 2 and 3 in the mineral-rich Macquarie Volcanic Province. Analysis of conodont biofacies data supports an enhanced understanding of the geological evolution of the Macquarie Volcanic Province by interpreting the interplay between volcanic activity and carbonate deposition. Conodont studies in the Billabong Creek Formation of the Gunningbland area reveal the only known biostratigraphic succession in Australia that extends continuously from the middle Darriwilian to basal Sandbian. Three Late Ordovician (late Sandbian to early Katian) conodont biozones in the upper Billabong Creek Formation correlate precisely with carbonates of the Molong Volcanic Belt to the east. Revised stratigraphic definitions of the Billabong Creek and Gunningbland formations are provided. [ABSTRACT FROM AUTHOR]

The Cobar Supergroup is a package of Siluro-Devonian sedimentary, volcanic and volcaniclastic rocks in central New South Wales that underwent significant deformation during the Middle Devonian Tabberabberan Orogeny. The Cobar Supergroup, particularly within the Cobar Basin, constitutes one of the most mineral-rich rock packages in New South Wales, being endowed with Au, Cu, Pb, Zn and Ag, mainly in what are commonly referred to as Cobar-type deposits. Inconsistencies in the traditional stratigraphic interpretation of the area have led to a re-evaluation of its structural history, in particular the role of the Rookery Fault, which bounds the eastern side of the basin. Evidence suggests that that structure may dip to the east, rather than the west, as is traditionally assumed, leading to the possibility that Tabberabberan deformation in the area took the form of a west-verging fold-thrust belt. Analogue modelling is employed to examine the consequences of that scenario. Such a mechanism explains the known distribution of stratigraphic units of the Cobar Supergroup and its basement, as well as observed structures, in particular a high strain zone immediately west of the Rookery Fault. The modelling indicates that deeper parts of the crust were thrust up along the Rookery Fault, which, along with substantial burial, led to perturbation of the geotherm and heating of the footwall. This accounts for the higher metamorphic grade immediately west of the Rookery Fault. Furthermore, heating and overpressuring of basement rocks in the footwall led to mobilisation of metal-bearing fluids and transport of them along the high strain zone and subsequent deposition of those metals within favourable structural traps, with variable interaction with basinal fluids, to form Cobar-type deposits. A fold-thrust mechanism with ongoing erosion of the thrust wedge can also explain the distribution of Middle to Upper Devonian rock sequences in the region. A west-verging fold-thrust model is proposed to explain Tabberabberan deformation of the Cobar Supergroup and its basement. Analogue modelling is employed to demonstrate the fold-thrust model. A fold-thrust model explains the distribution of Ordovician to Upper Devonian stratigraphic units in the Cobar region, as well as associated structures, metamorphic grade distribution and the origin of syn-deformational Au, Cu, Pb, Zn, Ag mineral deposits. [ABSTRACT FROM AUTHOR]

Neither the age nor the origin of the Parramatta River of coastal central New South Wales, Australia is well understood. Despite previous assertions, there is no evidence that the river is underfit or that its drainage pattern has experienced radical rearrangement. Yet the river ignores the obvious route to the sea at Botany Bay, perhaps because its course was set by the Oligo-Miocene when local drainage was realigned in response to the subsidence of the Botany Basin. Similarly anomalous is the river's route through the Hornsby Plateau to the ocean at Port Jackson. This is the result of antecedence, with the river pre-dating the upwarping of the plateau and maintaining its course across an uplifting surface. Two topographically distinct suites of drainage channels are preserved offshore. The earlier is traceable to depths of 260 m and is continuous with modern terrestrial drainage along the Hawkesbury River—the preservation of these channels may be a result of the subsidence of the east Australian margin since the Eocene. The more recent channels extend to depths of 120 m. These may post-date the earliest Oligocene when global sea levels fell by ≫50 m, resulting in intermittent exposure of the continental margin arising from glacio-eustatic oscillations in sea level. Deeper and older paleodrainage is absent offshore of Port Jackson and Botany Bay. Drainage along the proto-Parramatta River thus cannot pre-date the earliest Oligocene and it was only with the subsidence of the Botany Basin in the Oligo-Miocene that terrestrial drainage was realigned to the coast and channels were entrenched across the inner shelf. Sediments representative of a major flow-line sub-parallel to the path of the modern Hawkesbury–Nepean pre-date the uplift of the Blue Mountains Plateau and the upwarp of the Hornsby Plateau. These confirm the long-term role of the Hawkesbury–Nepean–Warragamba as the regionally dominant drainage line. There is no evidence that the Parramatta River is underfit or that it has experienced radical rearrangement. The lower part of the Parramatta River is antecedent, existing prior to the upwarping of the Hornsby Plateau. An older suite of submarine channels may preserve evidence of terrestrial drainage along the Hawkesbury River since the Eocene; a younger suite may post-date the earliest Oligocene when falling global sea levels resulted in the intermittent exposure of the continental margin. The Parramatta River is likely to have originated in the Oligocene. [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 central Lachlan Orogen volcanic belt contains predominantly silicic and explosive eruptive products emplaced between ca 428 and 412 Ma within elongate basins over an area ∼350 km long and 20 km wide. The volcanic rocks are exposed in two parallel, south-southeast-trending belts between Cobar and Albury, NSW, and have S-, I- or A-type magmatic affinities. The southernmost sequences include subaerial rocks of the Gurragong Volcanics and Walleroobie Volcanics (herein renamed the Gurragong Group), and the newly described Culcairn Group. The Gurragong Group comprises crystal-rich Walleroobie Ignimbrite, lithic-rich Corella Ignimbrite, Mount Ariah Rhyolite coherent facies and newly recognised airfall Indarra Tuff. The Culcairn Group includes the Budginigi and Wallandoon ignimbrites. The Budginigi Ignimbrite includes crystal-rich ignimbrite, the Hadrells Hill Member hyaloclastite breccia and the Soldiers Quarry Member (coherent rhyodacite). The Wallandoon Ignimbrite is compositionally intermediate, metaluminous and amphibole-bearing. The volume estimate of southern pyroclastic units ranges from 15 to 75 km3 per succession. The northern volcanic sequences include the Canbelego-Mineral Hill Volcanic Belt, Mount Hope Group and Ural Volcanics, all deposited in a shallow- to deep-marine environment during the Cobar Basin opening. The subaerial depositional environment of the southern volcanic successions, the proximity of exposed Silurian granitoid, and contact metamorphic overprint of the Devonian volcanic successions by contemporaneous intrusions implies the volcanic pile was thicker, and synchronous uplift was occurring. Variation in the aluminium saturation index from peraluminous to metaluminous, and a variation in high-field-strength elements in the almost exclusively felsic igneous rocks may reflect variation in the source rocks and temperature of partial melting. The resulting metallogenic patterns reflect these basement differences. Metals in the south resulted in intrusion-related Sn–W; in the north, the marine environment proximity to a major transcrustal structure and variation in the fertility of the lower crustal rocks led to the development of diverse mineral systems. The central Lachlan Orogen Siluro-Devonian volcanic belt is predominantly silicic, containing explosive eruptive products emplaced within a series of elongate basins between Cobar and Albury, NSW. The southernmost sequences, the Gurragong Group and the newly described Culcairn Group are subaerial; the northern sequences include the Canbelego-Mineral Hill Volcanic Belt, Mount Hope Group and Ural Volcanics and are wholly submarine. Variations in the igneous rock chemistry and regional mineralisation reflect the variation in the basement source rocks, related fertility and associated structures. [ABSTRACT FROM AUTHOR]

Late Ordovician conodonts (14 species), corals (five species) and stromatoporoids (two labechiid species) have been recovered from the carbonate intervals intersected in three drill holes in the area located immediately west and northwest of Peak Hill in central New South Wales. The WNDD0001 drill-core section consists of dominantly calcareous and clastic sedimentary rocks in the upper part and andesites in the lower part. The conodont fauna from the carbonate interval at the top confirms an early Katian age (Taoqupognathus blandus Biozone). The WNDD0002 drill-core section is composed of primarily carbonates in the lower part and dolomitic siltstones and sandstones in the upper part, which have been intruded by andesitic dykes and sills. A distinctive rugose coral species (Favistina plus) occurring in the carbonate interval towards the base of the section indicates a middle Katian age (Taoqupognathus tumidus-Protopanderodus insculptus Biozone). Therefore, the entire WNDD0002 drill-core section is stratigraphically higher than the drill-core section WNDD0001 to form the most complete Upper Ordovician sedimentary succession (unnamed formation) from the northern part of the Junee–Narromine Volcanic Belt. A correlative tabulate coral assemblage of middle Katian age was also recovered from the carbonates in the lower part of the GAMD0001 drill-core section. These new data demonstrate that the Upper Ordovician marine shelf sedimentary facies within these drill holes are comparable with those known from Gunningbland area farther south, a new finding that is important for future geological mapping and mineral exploration in the region. For the first time, a Late Ordovician conodont, coral and stromatoporoid fauna is recorded from the northern Junee–Narromine Volcanic Belt in NSW. A wide subsurface distribution of an Upper Ordovician marine shelf succession is confirmed in the region. New biostratigraphic data essential for the future geological mapping and mineral exploration are given for the area. [ABSTRACT FROM AUTHOR]

The orientation, petrography and geochemistry of numerous basaltic dykes between Kiama and Gerroa were investigated in this study. Geochemical analysis shows that the dykes range from sub-alkaline to alkaline in composition. The dykes fit into three distinct geochemical groups, with most being transitional from alkali basalts to foidites, followed by alkali basalts and lastly andesites/basaltic andesites. We suggest that three intrusive episodes occurred based on petrographic analysis and geochemical classification. The dykes contain phenocrysts of olivine, plagioclase and clinopyroxene in a fine-grained groundmass. Multiple microtextures were found, including porphyritic, glomeroporphyritic, amygdaloidal, aphanitic and intergranular. Most dykes strike northwest–southeast, two strike east–west, and four strike northeast–southwest. One dyke to the south of Boat Harbour Reserve contains numerous xenoliths, including gabbroic, granitic and charnockitic types. The gabbroic xenoliths were likely sourced from the mid-crust, whereas the granitic xenoliths were likely derived from the upper crust. Joints in the study area strike northwest–southeast, north–south, east–west and northeast–southwest. The dominant joint set strikes northwest–southeast, and secondary joint sets strike northeast–southwest. The least pervasive joint sets strike east–west and approximately north–south. The dykes intruded along long-lived inherent structural weaknesses in the host rocks, as their orientations match the orientations of dominant joint sets. Geochemically, the dykes are distinct in having an abundance of foidites, which are rare within the Sydney Basin. They are clearly different from the nearby upper Permian K-rich Gerringong Volcanics, but many of the alkali basaltic dykes are like those of the Sydney Basin, and the foidites are similar in composition to the lower Eocene Kulnura basalt on the NSW Central Coast. The orientation, geographic distribution and geochemistry of the dykes strongly suggest that the basaltic magmas have been injected through the same upper-crustal weaknesses over a protracted period. Dykes occurring between Kiama and Gerroa fall under three separate geochemical groups: alkali basalts to foidites, alkali basalts and andesites/basaltic andesites. Three intrusive episodes occurred based on petrographic analysis and geochemical classification. The dykes intruded along long-lived inherent structural weaknesses in the host rocks. [ABSTRACT FROM AUTHOR]

Paleomagnetic studies in the Lachlan Orogen have indicated rotation of elements within it, but the evidence for rotation is limited and has significant statistical uncertainty. This study presents a detailed paleomagnetic investigation, assisted by X-ray analysis of magnetic mineralogy of middle Cambrian to lower Silurian sedimentary and igneous rocks in Victoria and New South Wales. Four demagnetisation behaviours (types A, B, C and D) have been recognised. Type A is characterised by a single component, resulting in an approximately linear path over the magnetite unblocking temperature range. Type B specimens exhibit slow progressive demagnetisation over a wide temperature range, with clustering of demagnetised directions above the magnetite Curie temperature, indicating hematite. Behaviour C is also characterised by clustering of directions, but this extends over a wider temperature range. Samples with behaviour D show noisy and non-informative demagnetisation, indicating very low magnetic stability. Hysteresis data confirm that samples with behaviour B and C have high coercivities and remain unsaturated above 300 mT. Mineral liberation analysis of selected samples indicates presence of iron oxides, magnetite, titanomagnetite, botryoidal hematite and iron hydroxides. Only three sites yielded specimens with type A primary magnetisation, with a poorly defined pole from the Dookie Volcanics on the central limb of the orocline, which does match a previous result from the same district. Two paleopoles, of type B and C specimens from the rocks in Tabberabbera Zone and the Rockley Volcanics, plot within the confidence limit of poles defining the late Silurian to Early Devonian Australian apparent polar wander path. These poles match other poles representing Devonian overprints around the margins of the Lachlan Orogen that have been interpreted to be the result of alteration mineralisation produced by fluids driven by tectonic compression during events in the Bindian (420–410 Ma) or early Tabberabberan (405–380 Ma) orogenies. Paleomagnetic techniques have been used to test the rotation within the elements of the Lachlan Orocline in southeast Australia. Results suggest that the original remanence in the rocks is obscured owing to post-deformation overprint. This overprint is widespread in the Lachlan Orogen and is associated with the deformation during Bindian/Tabberabberan orogenic events. [ABSTRACT FROM AUTHOR]

Preservation of pre-Cenozoic porphyry Cu deposits requires geological events that bury the deposits before significant exhumation. Burial may be due to basin development over the top of the porphyry system or to burial beneath thrust sheets. The porphyry Au–Cu deposits in the Cadia district of central New South Wales underwent both events, and thus this metal-rich part of the crust survived the overprinted tectonic events that shaped eastern Australia. The Cadia porphyry Au–Cu deposits are associated with the Upper Ordovician to lower Silurian Cadia Intrusive Complex emplaced into the Upper Ordovician to lower Silurian Forest Reefs Volcanics and Middle Ordovician Weemalla Formation during the final phase of Macquarie Arc magmatism. Published stratigraphic evidence suggests west-northwest-striking faults influenced stratigraphic facies and thicknesses in the Forest Reefs Volcanics. Generally north- to east-northeast-striking faults that developed early in the district's history are likely a product of exhumation of the porphyry Au–Cu deposits and their host rocks during and after the Benambran Orogeny. Alteration halos of several of the porphyry Au–Cu and skarns were exhumed at this time. Later during the Silurian (Wenlock to early Ludlow), the partially exhumed porphyry systems were buried beneath sediments, correlated with the Waugoola and Mumbil groups, in a rift–sag basinal sequence deposited initially in local fault-bounded basins that must be connected regionally to formation of the Cowra and Hill End troughs to the west and east, respectively. This basin geometry was controlled by the reactivation of the extant basement faults. Shortening of the Silurian sedimentary succession during younger Paleozoic orogenies was accommodated in thin-skinned fold and thrust faults forming a complex network of bedding-parallel detachments, ramps and anticlines that are linked to steeply dipping reverse and oblique-reverse slip faults in the underlying Forest Reefs Volcanics and the Cadia Intrusive Complex. The world-class porphyry Au–Ci deposits were initially exhumed for a relatively brief interval during the early Silurian as a result of the Benambran Orogeny. The porphyry Au–Cu deposits were subsequently buried beneath Silurian sediments of the Waugoola Group accumulating in rifted basins formed during the Wenlock and Ludlow epochs of the Silurian, with sedimentary deposition continuing into the Pridoli (latest Silurian) in the lower part of the Mumbil Group. The Silurian basin was inverted with thin-skinned fabrics in the Silurian sedimentary rocks and thick-skin fabric localised along pre-existing faults, burying the deposits. [ABSTRACT FROM AUTHOR]

The Northparkes district, central New South Wales, hosts several economic Cu–Au deposits associated with discrete, thin, porphyry intrusive complexes emplaced in the Late Ordovician during formation of the Macquarie Arc. The recently discovered Two-Thirty Cu–Au–(Mo) prospect is a mineralised magmatic–hydrothermal breccia complex that is hosted by the moderately east-dipping Goonumbla Volcanic Complex on the western limb of the Milpose Syncline ∼15 km south of the Northparkes porphyry district. Generation of the magmatic–hydrothermal breccia complex is interpreted to be related to the 448.0 ± 4.4 Ma emplacement of the Two-Thirty porphyry. However, Re–Os dating of molybdenite from the breccia complex indicates a potential for a ca 440 Ma mineralising event that has similar timing to economic porphyry mineralisation in the Northparkes district. The discovery of the Two-Thirty prospect has important implications for exploration in the Northparkes district and the broader Macquarie Arc. Two-Thirty is only the second known occurrence of magmatic-hydrothermal breccia-hosted mineralisation discovered within the Macquarie Arc, with the other being Cadia Quarry. Mineralisation at Two-Thirty is potentially older than the Northparkes and Cadia deposits, and younger than the epithermal and calc-alkaline deposits at Cowal, Marsden and Ridgeway. The Two-Thirty is a polyphase magmatic–hydrothermal breccia complex that hosts Cu–Au (Mo). The Two-Thirty is the first significant breccia-hosted mineralisation found in the Northparkes district. U–Pb zircon crystallisation ages of the causative intrusion at Two-Thirty pre-date mineralisation at Northparkes. Re–Os dates of molybdenite from the Two-Thirty breccia complex are coeval with syn-mineralisation at Northparkes, supporting the model of periodic release of melts and fluids from underlying magma chambers during the formation of porphyry mineralisation in the Northparkes district. [ABSTRACT FROM AUTHOR]

The year 2020 marked the 200th anniversary of European settlers first encountering the 'noble expanse of water' of Lake George in New South Wales. Since 1820, unofficial observations and official measurements of the lake's water-level have been recorded almost continuously by various individuals, research teams, government departments and private companies. The lake's recent hydrographic history has been characterised by periods of flood and drought, which correspond with the prevailing climate conditions of SE Australia. This is the longest water-level record of its sort in the Southern Hemisphere and hence of great scientific and historic value. Here, we have compiled all available historic water-level data for Lake George, referenced them to common datums and presented a methodology for continuing the record using satellite imagery in lieu of on-site measurements. The 200-year water-level record of Lake George, NSW has been compiled and referenced to a common datum. This is the longest record of its type in the South Hemisphere, documenting the modern periods of flood and drought in southeastern Australia. Water levels for the period 1986–2019 when no on-site measurements were recorded have been estimated using satellite imagery and the lake's bathymetry. [ABSTRACT FROM AUTHOR]

Where tectonics is not a factor, the landscapes of granite batholiths show variations in average pluton elevation that follow each pluton's composition very closely. The granitoids of the Kosciusko and Maragle batholiths in the Highlands of southeastern New South Wales have clearly been influenced by tectonics. Examination of the relation between composition and mean pluton elevation reveals that the plutons of these batholiths lie in two groups, a Highlands group between the Jindabyne-Barney's Range Thrusts and the Tumut Ponds Fault Zone and a Western group west of the Tumut Ponds Fault Zone. Composition and mean pluton elevation are strongly correlated within each group, indicating they have been uplifted as two coherent blocks along those two fault systems. The plutons of the Berridale Batholith east of the Highlands form a contrasting low-relief group. Pluton mineralogy determines elevation across a granite batholith. Kosciusko Highlands were uplifted as one block along the Jindabyne Thrust and Tumut Pond Fault Zone. [ABSTRACT FROM AUTHOR]

Edenopteron, with a lower jaw some 48 cm long, and total length perhaps exceeding 3 m, is the largest Devonian lobe-fin known from semi-articulated remains. New material described from the type locality (Boyds Tower, south of Eden) includes three slightly smaller articulated skulls and jaws, and additional bones of the shoulder girdle. Another articulated skull roof, shoulder girdle and palate is described from a second locality (Hegarty Bay), about 10 km south of Boyds Tower. Both localities represent the upper part of the Worange Point Formation, of late Famennian age (uppermost Upper Devonian). The new morphological evidence supports a close relationship to the tristichopterids Mandageria and Cabonnichthys, from the slightly older (Frasnian, Upper Devonian) fossil fish assemblage at Canowindra, New South Wales. Features of the shoulder girdle (supracleithrum, anocleithrum) suggest that Edenopteron is more closely related to Mandageria than Cabonnichthys. Eight characters are used to define a tristichopterid subfamily Mandageriinae, to which Notorhizodon from the Middle Devonian of Antarctica is also referred. The Mandageriinae is endemic to East Gondwana (Australia–Antarctica). In combination with possibly the most primitive tristichopterid, Marsdenichthys from the Frasnian of Victoria, these distributions implicate East Gondwana as a likely place of origin for the entire group. This relates to the major but unresolved question of a possible Gondwana origin for all the land vertebrates (tetrapods). An endemic Gondwanan sub-group (Mandageriinae) of the Devonian fishes closest to land animals (tetrapodomorph tristichopterids) is confirmed. Retention of primitive features (e.g. accessory vomers) points to an earlier origin of the Mandageriinae in East Gondwana, consistent with the Victorian occurrence of another primitive tristichopterid (Marsdenichthys). Edenopteron is confirmed from a second south coast fossil site, and new characters indicate its closest relative is Mandageria from Canowindra, NSW. Congruent evidence of older Gondwanan occurrences in other groups (basal tetrapodomorphs, rhizodontids, canowindrids), and previously dismissed trace fossil evidence (Grampians trackways), implicate South China and East Gondwana as the likely place of origin for all land vertebrates. [ABSTRACT FROM AUTHOR]

Within the Lorne Basin, Mesozoic granitoid plutons and dacitic to rhyolitic extrusions form extensive components in a faulted, eroded Triassic sedimentary basin. Late Cenozoic plugs and flows of evolved basalts represent easterly extensions of the eroded Comboyne Volcano. The basin marks a terminal outpost of the New England Orogen, much modified by later alkaline felsic intrusions and flow remnants. Many origins are invoked for its tectonic genesis and magmatic evolution including plate tectonic, caldera and even meteoritic impact events. This review uses extended field study, zircon fission track, K–Ar and Ar–Ar age-dating, petrography and geochemical analyses on igneous suites. These results are combined with previously published and unpublished studies to clarify relationships between volcanic and plutonic suites, structural features and paleotopographic developments, allowing for an enlarged synthesis of Lorne Basin magmatism and its tectonic contexts. Dating reveals rhyodacitic volcanism began at ca 221 Ma (Milligans Road) and culminated in emplacements of I- and A-type dioritic to granitic suites (North Brother, Middle Brother) at ca 217–212 Ma (MAGMATIC EPISODE 1, late Triassic). Voluminous alkaline rhyolitic feeders and flows (Bago Range, Batar Creek) erupted between ca 187 and 160 Ma (MAGMATIC EPISODE 2, early–mid-Jurassic). Lavas infilled extended drainages cut into a dissected, faulted terrain and disrupted former drainage patterns. An alkaline monzodioritic to granitic pluton and late-stage rhyolitic dyke swarm (South Brother) were emplaced at ca 126 and 119 Ma (MAGMATIC EPISODE 3, early Cretaceous). This chemically distinct magmatism coincided with thermal coastal faulting along eastern Australia. A large eroded plug and dyke complex (Mount Lorne) shows steep flow banding and lies within dissected radial flow infillings. This prominent eruptive conduit tapped a significant ring fault system. Although undated, its petrography resembles features related to MAGMATIC EPISODE 3. The study revealed a far greater profusion of rhyolitic feeders and flows than previously thought, making likely volcanic volumes within episodes difficult to estimate. The youngest volcanic remnants infill later drainages, are dated between ca 17 and 13 Ma (MAGMATIC EPISODE 4, mid-Neogene), and are evolved derivatives related to the adjacent Comboyne central volcano. Some evolved basalts contain feldspathic and mafic crystallisations indicating mid-crustal melt processes. These bimodal suites represent a traverse over an asthenospheric plume during northward lithospheric migration of eastern Australia. Minor vitrophyric bodies recorded across the Lorne Basin only intrude Carboniferous basement beds. Their origin and age are enigmatic and represent a final puzzle to solve in the evolution of Lorne Basin magmatism. [ABSTRACT FROM AUTHOR]

This study investigates the prospectivity for porphyry Cu mineralisation of the early Paleozoic Loch Lilly-Kars Belt, which follows the southern margin of the Paleoproterozoic Broken Hill (Willyama) Inlier in western New South Wales, Australia. The belt is thought to have resulted from the 515–510 Ma collision of a volcanic passive margin and an intra-oceanic island arc above a west-dipping subduction zone, with subsequent post-collisional magmatism. To identify fertility signals of selected magmatic intrusive rocks, we combined whole-rock analyses with in-situ zircon trace-element and isotopic measurements. Data reveal that both Cambrian (ca 496 Ma) and Devonian (ca 393 Ma) intrusive suites are present in the Loch Lilly-Kars Belt. Cambrian dioritic rocks are largely non-fertile for porphyry Cu mineralisation, whereas Devonian monzodiorites and monzonitic porphyries carry strong fertility signals that include high whole-rock Sr/Y (>35) and V/Sc (>10) values, associated with the occurrence of equant, stubby zircons showing relatively constant Eu/Eu* values without any significant Eu anomalies. Although only few samples were analysed and more intensive exploration is required, the results of this study indicate significant potential for porphyry Cu mineralisation in this poorly known belt. [ABSTRACT FROM AUTHOR]

Black opal (opal-AG) owes its dark coloration to a fine-grained pigment commonly inferred to be mainly carbon, yet chemical compositions for black opals suggest there may be additional components. Here we search for such components in pigment concentrates prepared by dissolving black opal nodules (nobbies) from Lightning Ridge (NSW) in hydrofluoric acid, using electron microscopy (scanning electron microscopy, transmission electron microscopy), X-ray diffraction and laser-ablation ICP-MS. The results demonstrate the presence of sulfides—predominantly pyrite and chalcopyrite, with minor galena and Ti-oxide phases, as additional components of the pigment. ATR-FTIR analysis indicates the presence of C=O and C–H groups, consistent with an organic origin. Transmission electron microscopy images of pigment show variously deformed, originally spherical ∼100 nm particles rich in sulfide and carbon, which are interpreted as thin coatings of pigment on now dissolved opaline silica spheres. Laser-ablation ICP-MS analysis identifies remnant silica in pigment concentrates, which may be interpreted as opaline silica surviving HF treatment protected as inclusions in sulfides. When examined within the context of petrographic observations from more than 1000 opal nodules (nobbies) at Lightning Ridge, these new results suggest that pigment carbon and sulfides in the nodules formed microbially under initially anoxic groundwater conditions, within pre-existing cavities concurrently being filled with silica sol ultimately derived from chemical weathering of feldspar-rich volcaniclastic sediment. Intensely black pigment layers observed at the floor of many nodules indicate settling of dark, high-density (sulfide–Ti-oxide-rich) pigment within cavities, with the implication that sulfate-reducing bacterial (SRB) activity commences early during the silica sol-gel ripening process. Microbial activity may persist until after the cavity has completely filled with the silica sol, as illustrated by abundant black opals with uniformly distributed pigment. Pigment formed at this stage may no longer be able to settle out within the ripening and increasingly viscous silica gel, thus forming pigmentation throughout the opal cavity. The existence of 'amber', pigment-poor opal with intensely black basal pigment layers is interpreted as signalling a lack of sulfate to sustain further SRB activity, or a change to more oxidising conditions, possibly related to interaction with surface waters within a downward-penetrating weathering front. A change in redox conditions would shut off activity of SRB and thus sulfide pigment production and allow development of aerobic microbial activity as described by others. [ABSTRACT FROM AUTHOR]

The Ordovician Daylesford Limestone at Bowan Park and the Fossil Hill Limestone at Cliefden Caves have diagenetic and pedogenic features of microkarst, paleosols and calcrete associated with subaerial disconformities in their stratigraphic sequences, all of which, as an ensemble, have global geoheritage significance. The original shelly limestones, lime mudstones, and coralline limestones have selectively dissolved to form vugular limestone whose cavities have filled with sparry calcite and/or crystal silt. The limestones also have been calcretised to develop massive and laminar calcrete and calcrete ooids. Below disconformity surfaces are bleached limestone, crystal-silt and spar-filled fossil moulds and enlarged moulds, micro-breccia-filled moulds and fissures filled with crystal silt, calcrete pellets and calcrete ooids. The disconformity surfaces are irregular or undulating interfaces between lithologies, fissures and fissure-fills, and calcrete. Above disconformities there are limestone lithoclasts, remanié fossils, calcreted limestone, veined limestone, calcrete ooids, laminated calcrete, lithoclast grainstone, or calcrete-ooid grainstone, and lithoclasts with fossils moulds filled with crystal silt and/or spar. The lithological, stratigraphic and possibly landscape differences, make the subaerial diagenesis/pedogenesis in the Daylesford Limestone subtly different to that of the Fossil Hill Limestone. Subaerial disconformities and associated diagenesis/pedogenesis, as recorded in these formations, are not widely reported globally nor well represented in Ordovician limestones. The microkarst features provide insights into the types of subaerial diagenesis/pedogenesis during the Ordovician and into climate, landscape setting, paleohydrology, and groundwater/rainwater alkalinity. Consequently, the story of the Ordovician microkarst, paleosols and calcrete ooids is unique and globally of geoheritage significance as examples of subaerial alteration in an ancient high-rainfall, tropical climate volcanic island environment in a tectonically active region. [ABSTRACT FROM AUTHOR]

Globally significant geoheritage features of the Cliefden Caves area, in the Belubula River Valley between Orange and Cowra in central western New South Wales, comprise a richly fossiliferous shallow-water limestone succession of Late Ordovician age (the Cliefden Caves Limestone Subgroup) overlain by deep-water laminites and allochthonous limestones of the Upper Ordovician Malongulli Formation. Key features of the Ordovician geology of the Cliefden Caves area that have been identified using the Geoheritage Toolkit as being of international significance are the abundance of unique and exceptionally diverse fossils in the Fossil Hill Limestone (forming the lower part of the Cliefden Caves Limestone Subgroup), which supplement detailed interpretation of carbonate-dominated deposition within an Ordovician volcanic island setting. The fossiliferous limestones preserve biostromes and local small bioherms of stromatoporoids and corals, and recurrent in situ and disarticulated/imbricated Eodinobolus shell beds formed in shallow, quiet-water, dominantly muddy carbonate sediments that passed up-sequence to clay-free carbonate environments. These mud-dominated carbonate sediments are interspersed with higher-energy conditions, represented by skeletal, lithoclastic and calcrete-ooid grainstones overlying disconformities, leading to the identification of subaerial disconformities and associated diagenesis in the Fossil Hill Limestone. The Fossil Hill Limestone is succeeded by massive limestones in the middle part of the Cliefden Caves Limestone Subgroup and then, in turn by the Vandon Limestone and the deeper-water graptolitic laminites of the Malongulli Formation—this completes a succession that is rarely preserved in the geological record, further enhancing the geoheritage significance of the Cliefden Caves area. [ABSTRACT FROM AUTHOR]

The geology of New South Wales is diverse, spanning Paleoproterozoic to modern materials and their various associated landforms and soils. In recognition of the intrinsic geological value of the State, around 150 geological sites were nominated to the now defunct Register of the National Estate, with the objective of geoconservation. However, these sites did not encompass the full range of geology of New South Wales; neither did they offer registered sites any protection. Analysis shows that the types of sites nominated were biased towards sedimentary and igneous rocks, and fossils, with under representation of metamorphic rocks, site-restricted soils, geomorphology and hydrogeology. To test the utility of the Brocx and Semeniuk 'Geoheritage Toolkit', a subset of the Register listings was re-examined, focusing on the Sydney Basin. Within the Sydney Basin, 59 nominated sites were reassessed using various geoheritage categories and the hierarchical framework of scale of the Toolkit. Four sites within the Sydney Basin were found to have features of international to national significance, and to have national historical value. These sites will need to be renominated for State and National listing. Clearly, to ensure that University teaching sites, as well as stratigraphic and lithologic type sections and reference sites, reflecting the geodiversity of New South Wales are conserved for future generations, a greater number of sites need to be put forward for heritage listing. [ABSTRACT FROM AUTHOR]

The means and timing of the formation of Australian sediment-hosted precious opal remain a subject of continuing debate. In this study, the question of which water formed the opal is addressed by examination of rare earth element data for opals and host rocks. The available data, mainly for Lightning Ridge, NSW, suggest a positive Eu anomaly, relative to the neighbouring Sm and Dy, occurs in opals whereas no such anomaly was found for the weathered Cretaceous sediments hosting the opal. Such anomalies may be inherited from the source rock with a similar positive Eu anomaly or generated in situ by severe reduction. There is no indication of major reduction processes during the opal formation that could have led to such a Eu anomaly so this is likely inherited from a source rock. As the opal host rocks did not show this anomaly, the source rocks must be external to the opal fields. Calcite cements within rocks hosting the aquifers of the Eromanga and Surat basins of the Great Artesian Basin have been reported to have a positive Eu anomaly, which strongly suggests that opal was formed by upwelling Great Artesian Basin artesian waters. This work has also highlighted variations in trace-element concentrations in opals, which indicate significant variation in the source water composition during opal formation or different water sources were involved. Either of these is indicative of the source for the opal with its trace elements derived from external sources. These conclusions have significant implications to considerations of how opal formed, and hence, for the exploration for other deposits and to the chemistry and timing that led to the formation of opal. [ABSTRACT FROM AUTHOR]

Devonian fossil localities are summarised for coastal southeastern Australia, including both marine invertebrates representing a major late Frasnian (Late Devonian) transgression, and plant remains of Middle-Late Devonian age in associated non-marine strata. Lycopsid plant specimens (Leptophloeum) from near Majors Creek, NSW, first documented by Edgeworth David and E. F. Pittman in association with marine fossils to demonstrate a Late Devonian age, are illustrated for the first time. Lycopsid plants of presumed Middle Devonian age are illustrated from three new localities: Yowrie River inland from Cape Dromedary, Tuross River northwest of Narooma and Charlies Forest Road northeast of Braidwood. The Yowrie River occurrence (in float) indicates probable Middle Devonian strata upstream that are not shown on published maps. The Tuross River occurrence is in sheared and folded strata previously mapped as Ordovician, and the Braidwood occurrence demonstrates Devonian black shales adjacent to previously mapped Ordovician. Evidence supporting alternative thrust or simple fold interpretations for the Budawang Synclinorium is discussed, and relevant Ordovician fossil localities are listed. [ABSTRACT FROM AUTHOR]

More than 1000 near-circular mounds up to 40 m diameter and 2.1 m high, which contain 15-1250 m3 (mean 159 m3) of gravel, have been identified in western New South Wales. Mounds are more pebble-rich than the surrounding surface regolith and contain abundant pebbles to 1196 g weight. Resemblance to smaller gravel nest mounds of the malleefowl (Leipoa ocellata) suggests they were constructed by a similar although larger bird. Pebbles were inadvertently concentrated in the nest mounds during construction and maintenance. Formation by geological mechanisms, as burrow spoil or burial mounds is not compatible with the features of the mounds. The mounds are undated, but partial blanketing by eolian sand suggests they predate the Last Glacial Maximum. The mounds are now spatially associated with Casuarina trees. Pollen records in southeastern Australia reveal that shrub and grassland replaced Casuarina woodland as aridity increased after ca 35 000 yrs BP. Climate change driven habitat loss in the semi-arid zone likely caused the extinction of the apparently Casuarina woodland dependent megapode responsible for the gravel mounds. The mounds partly map the megapode distribution and provide an opportunity to date the local extinction of a megafauna member, compare this to climate and vegetation changes, and determine the duration of overlap with human occupation. [ABSTRACT FROM AUTHOR]

The Coolac Serpentinite, in the Tumut region of southeastern NSW, is one of many Alpine-type, linear ultramafic bodies exposed in the Lachlan Orogen of New South Wales. Despite the significance of such oceanic lithosphere throughout the orogen to tectonic models, few studies on the genesis of these bodies in the Lachlan Orogen have been documented. A significant proportion of the Coolac ultramafic rocks are only partially serpentinised, making them good candidates for detailed petrological and geochemical studies. The Coolac peridotites include harzburgites with mineral compositions and bulk-rock REE concentrations similar to abyssal peridotites. Assuming depleted mantle compositions, HREE concentrations are limited (0.2-0.3 × primitive mantle) implying melt extraction of 15-20%. Conversely, some Cr-spinel data within the harzburgites (Cr# = 0.22-0.27) indicate partial melting of only 9-11%. Adsorbed mantle pyroxenes, excess olivine and LREE enrichment suggest melt-rock interactions led to the refertilisation of the harzburgites. Isotope characteristics of a ca 501 Ma allochthonous tonalite block derived from melting of altered oceanic crust and a ca 439 Ma oceanic granite intrusion indicate an identical source that separated from the fertile mantle at 660 Ma. This places chronological constraints on the harzburgites, which are the result of two-stage melting involving a lherzolite protolith formed during the break-up of Rodinia followed by harzburgite formation during a further melt extraction event within an extensional phase of the Delamerian Orogeny. The harzburgites were enriched via melt-rock interactions soon after formation as well as during phases of the Benambran Orogeny beginning at ca 439 Ma and ending around ca 427 Ma with the emplacement of the North Mooney Complex, a layered ultramafic-gabbro association that has characteristics of Alaskan-style intrusions similar to the Fifield complexes of the central Lachlan Orogen. [ABSTRACT FROM AUTHOR]

The Mullaley Sub-basin of the Gunnedah Basin extends from Quirindi in the southeast, to north of Narrabri, to west of Dunedoo in northern New South Wales. There have been more than 100 boreholes sunk to basement investigating the (lower Permian) Cisuralian coal and coal seam gas resources of the Mullaley Sub-basin since the early 1990s. A desktop review of this open file information has allowed the formal correlation and naming of six Cisuralian coal members attaining a maximum 35 m of cumulative thickness within an upward coarsening sedimentary package totalling no more than 150 m. In ascending order, the coal members are: Bibblewindi (0–10 m), Bohena (3–18 m), Collygra (0.5–3 m), Coxs (1.5–4 m), Tullamullen (0.5–4 m) and Mooki (0.5–3 m). Cisuralian coal seams in the Maules Creek Formation of the southern Mullaley Sub-basin are here correlated with those of the Greta Coal Measures at Werris Creek and Muswellbrook. It is apparent that basement paleotopography played a significant role in the Cisuralian coal development as coals are best developed where the sedimentary sequence is greater than 60 m thick, as there the thick seams (Bohena and Bibblewindi coal members) occur towards the base of the sequence. The maximum western limit of the Cisuralian coals (Rocky Glen Ridge) is further east than previously inferred with new drilling information showing the Porcupine Formation directly overlying the barren pelletoidal claystones of the Leard Formation or the underlying volcanics (Boggabri Volcanics/Werrie Basalt). Early marine transgressions at the top of the Maules Creek Formation have stopped development of the Mooki, Tullamullen and Coxs coal members in the northern and eastern Mullaley Sub-basin and allowed the development of localised paraconglomerate (diamictite) intervals up to 10 m thick. Thick (>20 m cumulative) coal occurrences are localised to the Jacks Creek and Pilliga East State Forest areas southwest of Narrabri. The coal resource potential of the Mullaley Sub-basin is estimated at 13–28 billion tonnes. [ABSTRACT FROM AUTHOR]

Eight dredges from the southern New South Wales continental slope sampled the offshore extension of the Lachlan Orogen. Two rock suites were recovered: (1) lower greenshist facies limestones, felsic volcanics, sandstones, mudstones and Moruya Suite granodiorite correlate with the onshore Silurian to mid-Devonian orogenic phase; and (2) a strongly deformed greenschist to lower amphibolite facies mafic volcanics, cherts, marbles, pelites and serpentinites correlate in part with the Cambro-Ordovician Wagonga Group of the Narooma Terrane. The mafic volcanic rocks have ocean island, tholeiitic and boninitic basalt affinities. The offshore distribution of ocean island basalt that correlates with medial Cambrian basalt breccias at Batemans Bay suggests a large seamount or seamount complex. The boninites, tholeiites and ultramafics could be part of a forearc-generated ophiolite. The Narooma Terrane basement is interpreted as the part of the bonititic arc postulated to have collided with Vandieland in late early Cambrian time. Mid-Cambrian rifting of the oceanward part of this arc remnant, generated the Albury–Bega Terrane oceanic basement exposed in the Howqua Valley in the west and Melville Point in the east. Overlying are upper–mid-Cambrian to lowermost Ordovician black shale and chert, Lower Ordovician to Gisbornian Adaminaby Group quartz turbidites and Gisbornian to lower Bolindian Bendoc Group black shales. Batemans Bay exposures are reinterpreted as a dismembered basin margin succession onlapping the west-facing attenuated flank of the Narooma Terrane. The Narooma Cambro-Ordovician cherts and mudstones were initially deposited outboard on the more elevated seamount flank elevated above the clastic-filled basin to the west. Benambran deformation commenced in latest Ordovician time uplifting the outer Narooma Terrane, shedding debris from the seamount and its flanks, culminating in allochthonous displacement of chert masses to the basin's eastern margin to Narooma, and emplacing them as a succession of thrust sheets. Contemporaneously, silt and mud of the Bogolo Formation, deposited from the west, were mixed with olistostomal basalt and chert debris from the east. Early Silurian westward tectonic transport of the Narooma Terrane ruptured the Albury-Bega basin floor at Batemans Bay, thrusting it and its sedimentary cover over its eastern margin as a series of thrusts each floored by melange (mapped Bogolo Formation), derived from the slope debris and its overpressured sedimentary cover. Offshore, the metamorphosed Benambran phase rocks are unconformably overlain by Tabberabberan cycle sediments and volcanics intruded by granodiorite. Our interpretation of the boundary between the Albury-Bega and Narooma terranes as a thrusted passive margin accumulation is incompatible with models of a Narooma Accretionary Complex formed by the subduction of the Paleopacific Plate. [ABSTRACT FROM PUBLISHER]

The Australian continent displays the most complex pattern of present-day tectonic stress observed in any major continental area. Although plate boundary forces provide a well-established control on the large-scale (>500 km) orientation of maximum horizontal stress (SHmax), smaller-scale variations, caused by local forces, are poorly understood in Australia. Prior to this study, the World Stress Map database contained 101 SHmaxorientation measurements for New South Wales (NSW), Australia, with the bulk of the data coming from shallow engineering tests in the Sydney Basin. In this study we interpret present-day stress indicators analysed from 58.6 km of borehole image logs in 135 coal-seam gas and petroleum wells in different sedimentary basins of NSW, including the Gunnedah, Clarence-Moreton, Sydney, Gloucester, Darling and Bowen–Surat basins. This study provides a refined stress map of NSW, with a total of 340 (A–E quality) SHmaxorientations consisting of 186 stress indicators from borehole breakouts, 69 stress measurements from shallow engineering methods, 48 stress indicators from drilling-induced fractures, and 37 stress indicators from earthquake focal mechanism solutions. We define seven stress provinces throughout NSW and determine the mean orientation of the SHmaxfor each stress province. The results show that the SHmaxis variable across the state, but broadly ranges from NE–SW to ESE–WNW. The SHmaxis approximately E–W to ESE–WNW in the Darling Basin and Southeastern Seismogenic Zone that covers the west and south of NSW, respectively. However, the present-day SHmaxrotates across the northeastern part of NSW, from approximately NE–SW in the South Sydney and Gloucester basins to ENE–WSW in the North Sydney, Clarence-Moreton and Gunnedah basins. Comparisons between the observed SHmaxorientations and Australian stress models in the available literature reveal that previous numerical models were unable to satisfactorily predict the state of stress in NSW. Although clear regional present-day stress trends exist in NSW, there are also large perturbations observed locally within most stress provinces that demonstrate the significant control on local intraplate sources of stress. Local SHmaxperturbations are interpreted to be due to basement topography, basin geometry, lithological contrasts, igneous intrusions, faults and fractures. Understanding and predicting local stress perturbations has major implications for determining the most productive fractures in petroleum systems, and for modelling the propagation direction and vertical height growth of induced hydraulic fractures in simulation of unconventional reservoirs. [ABSTRACT FROM PUBLISHER]

The ∼E–W-trending Olepoloko Fault and ∼ENE-trending Louth-Eumarra Shear Zone in north-central New South Wales are approximately orthogonal to the dominant ∼N–S-trending structural grain of Paleozoic eastern Australia. These structures have been interpreted to represent the boundary between the Thomson and Lachlan orogens, but their exact geometry and kinematics remain unclear owing to the scarcity of surface exposure. Using gridded aeromagnetic data and limited field mapping, we obtained new data on the tectonic history of the Louth-Eumarra Shear Zone, which seems to represent a broad zone of dextral shearing with a component of crustal thickening indicated by the recognition of kyanite growth in a mica-schist. The timing of deformation is relatively poorly constrained, but at least a component of the dextral shearing appears to be coeval or younger than the age of displaced late Silurian and Early Devonian granitoids. Additional indicators for dextral kinematics farther north, along the ∼ENE-trending Culgoa Fault, suggest that the width of the zone that was subjected to dextral deformation is possibly >100 km. This raises the possibility that a large component of dextral displacement was accommodated in this region. In a broader geodynamic context, we discuss the possibility that the precursor of the Louth-Eumarra Shear Zone and Olepoloko Fault originated from segmentation between the northern and southern Tasmanides, perhaps during the Cambrian. The existence of such a discontinuity may have buttressed the process of oroclinal bending in the Silurian. The observed dextral kinematics has possibly resulted from reactivated deformation during the Tabberabberan and Alice Springs orogenies. [ABSTRACT FROM PUBLISHER]

The formation of the northern part of the New England oroclines has previously been linked to dextral strike-slip faulting, but hitherto no concrete evidence has been shown to support this suggestion. We studied an exposure of a fault zone in the Red Rock headland, northeastern New South Wales, and we present here structural observations from the fault zone complemented by geochronological constraints on the timing of faulting and geochemical data that inform us on the nature of the co-seismic fluids. Our observations show evidence for dextral strike-slip faulting, with a reverse kinematic component, along a subvertical fault plane oriented NNE–SSW. Rb–Sr and40Ar/39Ar ages from fault gouge samples indicate that brittle faulting occurred at 286.5 ± 1.5 Ma with possible reactivations at 267.0 ± 9.6 Ma and 264 ± 11 Ma. Oxygen and hydrogen stable isotope geochemistry indicates that the fluids that circulated in the fault zone were associated with a deep crustal source. Based on these results, we conclude that the Red Rock Fault zone is likely an exposed segment of a larger fault system, that was active at 288–285 Ma (Early Permian). The timing of faulting was contemporaneous with the development of the New England oroclines, raising the possibility that oroclinal bending was accompanied by strike-slip faulting. Whether faulting was associated with local deformation at the limb of the Coffs Harbour Orocline, or with a larger-scale wrench tectonic zone remains unresolved. [ABSTRACT FROM PUBLISHER]

The Southern Highlands of New South Wales between Goulburn and Moss Vale have long been known to contain scattered deposits of bauxite associated with Paleogene basalts. They are currently the subject of an exploration licence held by Australian Bauxite Ltd. Mostly the bauxites overlie the basalt or unconsolidated sub-basaltic Paleogene sediments. Most previous studies suggest the bauxites are formed byin situweathering of the basalt. This study shows that all the bauxite deposits occur unconformably above pisolithic basalt, Paleogene sediments or weathered Paleozoic rocks, and that they contain materials only formed at or near the surface including poorly diffracting materials and maghemite. Most also contain significant quartz. Most bauxites also show signs that they have been chemically active over a long period with abundant gibbsite cements, pseudomorphs and void fillings as well as abundant hematite and goethite. These bauxites, like those at Weipa, are formed by the erosion, transport and deposition of bauxitic pisoliths in valleys as the landscape evolved. The pisoliths are inferred to have originated from weathered basalt profiles and have been concentrated by reworking. [ABSTRACT FROM PUBLISHER]

This work presents the first detailed sedimentary facies analysis of the subsurface latest Silurian to Early Devonian Winduck Interval, based on four wells in the Blantyre and western Neckarboo sub-basins in the central part of the Darling Basin. The study integrates wireline logs, cores, cuttings and limited biostratigraphic data to determine the sedimentary sequence subdivision in the study area. Sedimentological analysis was applied, using characteristic wireline-log responses, and core and cuttings descriptions, to aid in the development of a depositional environment model for the Winduck Interval. Twenty-nine sedimentary facies are defined, forming five facies associations. These associations are characterised as distributary channel sandstone complex, distributary mouth bar, tidal channel sand, proximal delta front associated with mouth bars complex, and distal delta front to prodelta sediments. Tectonism influenced the paleogeography, although fault zones (a complex of normal and reverse faults) were important in determining sedimentary sequence thicknesses obtained from the wells. Tectonic subsidence was moderate, and accumulation rates were low. The results of sedimentary facies analysis of the Winduck Interval have implications for evaluating the hydrocarbon potential, and may assist extensive exploration efforts that are currently occurring in the Darling Basin within western New South Wales. [ABSTRACT FROM PUBLISHER]