Sydney Basin Research Articles

Non-Additive Effects of Forest Litter on Flammability

Forest litter is a fuel component that is important for the propagation of fire. Data describing fuel load, structure and fuel condition were gathered for two sites of Sydney Coastal Dry Sclerophyll Forest, a common vegetation type in the Sydney Basin, Australia. Surface litter from the sites was sorted into its constituent components and used to establish which component or mixture of components were the most flammable using several metrics. A general blending model was used to estimate the effect the different mixtures had on the response of the flammability metrics and identify non-additive effects. Optimisation methods were applied to the models to determine the mixture compositions that were the most or least flammable. Differences in the flammability of the two sites were significant and were driven by Allocasuarina littoralis. The presence of A. littoralis in litter mixtures caused non-additive effects, increasing the rate of flame spread and flame height non-linearly. We discuss how land managers could use these models as a tool to assist in prioritising areas for hazard reduction burns and how the methodology can be extended to other fuel conditions or forest types.

Australia's earliest tetrapod swimming traces from the Hawkesbury Sandstone (Middle Triassic) of the Sydney Basin

AbstractThe Hawkesbury Sandstone (Hawkesbury Series, Sydney Basin) on the southeastern coast of New South Wales, Australia, preserves a depauperate but important vertebrate tetrapod body-fossil record from the Early and Middle Triassic. As with many fossil sites around the world, the ichnological record has helped to shed light on the paleoecology of this interval. Herein, we investigate historical reports of a trackway pertaining to a putative short-tailed reptile found at Berowra Creek in the 1940s. Reinvestigation of the surviving track-bearing slabs augmented by archival photographs of the complete trackway, suggests that these impressions, which consist primarily of didactyl tracks (plus less common monodactyl and tridactyl traces), represent the earliest example of a swimming tetrapod found in Australia. Another isolated specimen (possibly from a nearby locality at Annangrove) appears to represent similar didactyl swim traces of a second, larger individual. Although the identities of the trackmakers are unknown, the Berowra Creek individual had an estimated body length of between ~80 cm (short-coupled) and 1.35 m (long-coupled), and produced the subaqueous trackway while travelling upslope (against the current) on a sandbar within a braided river system of the Hawkesbury Sandstone. These trackways partially resemble amphibian swim traces in the so-called Batrachichnus C Lunichnium continuum, but appear to represent a unique locomotion trace. This reanalysis of the Berowra Creek trackway provides insight into the locomotion of tetrapods of the Triassic Hawkesbury Series, which remains a poorly understood aspect of their life history.

Investigation into the utility of flying foxes as bioindicators for environmental metal pollution reveals evidence of diminished lead but significant cadmium exposure.

Due to their large range across diverse habitats, flying-foxes are potential bioindicator species for environmental metal exposure. To test this hypothesis, blood spots, urine, fur, liver and kidney samples were collected from grey-headed flying-foxes (Pteropus poliocephalus) and black flying-foxes (P. alecto) from the Sydney basin, Australia. Concentrations of arsenic, cadmium, copper, lead, mercury and zinc and 11 other trace metals were determined using inductively coupled plasma mass spectrometry. As predicted, kidney and fur lead concentrations were lower compared to concentrations found in flying-foxes in the early 1990’s, due to reduced environmental lead emissions. Tissue cadmium concentrations in flying-foxes were higher compared to previous studies of flying-foxes and other bat species, suggesting that flying-foxes were exposed to unrecognized cadmium sources. Identification of these sources should be a focus of future research. Urine concentrations of arsenic, cadmium, mercury, and lead were proportional to kidney concentrations. Given that urine can be collected from flying-foxes without handling, this demonstrates that many flying-foxes can be assessed for metal exposure with relative ease. The analysis of blood spots was not viable because of variable metal concentrations in the filter paper used. Fur concentrations of metals correlated poorly with tissue concentrations at the low levels of metals found in this study, but fur could still be a useful sample if flying-foxes are exposed to high levels of metals. Lastly, heat inactivation had minimal impact on metal concentrations in kidney and liver samples and should be considered as a tool to protect personnel working with biohazardous samples.

Isotopically enriched n-alkan-2-ones with even chain predominance in a torbanite from the Sydney Basin, Australia

n-Alkan-2-ones (methyl ketones) ranging from C14 to C31, were recovered from the polar fraction of an extract of a torbanite from the Sydney Basin, Australia. There was a very slight even-over-odd predominance between C20 and C24n-alkan-2-ones, together with remarkably high contents of the C24, C26 and C28 homologues. A range of C16 to C28 macrocyclic alkanes, as well as their corresponding methylated counterparts (C19–C24), was also detected in the saturate fraction obtained after molecular sieve treatments. Due to the relatively high contents of the n-alkan-2-ones and macrocyclic alkanes, we were able to carry out GC–irMS analysis to determine the δ13C values of specific compounds. The even-numbered n-alkan-2-ones from C24 to C28 were significantly 13C-enriched, compared to the other n-alkan-2-ones, which had similar isotopic values to the macrocyclic alkanes. The majority of the n-alkan-2-ones detected here probably had the same algal source as the macrocyclic alkanes, which is likely to be lipids and algaenan of the green microalga Botryococcus braunii. However, the distribution and 13C enrichment of C24, C26 and C28n-alkan-2-ones indicates that an additional source must be present.

Modelling Hazardous Reduction Burnings and Bushfire Emission in Air Quality Model and Their Impacts on Health in the Greater Metropolitan Region of Sydney

Modelling and forecasting of air pollution from bushfires or hazardous reduction burnings is important in providing information and allowing measures to be taken to reduce the exposure of people from harmful effect of air pollutants from fire events. In this work, the meteorological, chemical transport model and air quality models developed by the Commonwealth Scientific and Industrial Research Organisation of Australia are used in conjunction with the smoke emission model to simulate the formation and dispersion of particle aerosols (PM2.5) in the Greater Metropolitan Region of Sydney as the results of emission of different pollutant species from hazardous reduction burnings or from bushfires. The smoke emission model is based on a fire model describing two distinct fire behaviours: flaming and smothering. There are several schemes that can be used to estimate the emission factors of different emitted species from fire of various vegetation types. A comparison of these schemes is performed by comparing the air quality model output from air quality model with observation from monitoring stations in a case study, the May 2016 prescribed burning winter period, which caused elevated particle concentrations in the Sydney basin. The PM2.5 prediction over the Greater Metropolitan Region of Sydney from the forecasting modelling tool will then be used to calculate the population exposure and health impacts due to the May 2016 fire event as a case study. The three main health endpoints considered for health impacts are mortality, respiratory-related and cardiovascular hospitalisations. The results are comparable with other studies using non-modelling methods of determining the exposure and health impacts on this event.

First record of a petrified gymnospermous wood from the Kungurian (late Early Permian) of the southern Sydney Basin, southeastern Australia, and its paleoclimatic implications

For the first time, a silicified wood with well-preserved inner structures is reported from the Kungurian (Early Permian) Snapper Point Formation in the southern Sydney Basin, southeastern Australia. It is characterized by uni- to tetraseriate araucarian radial tracheidal pits and large, simple cross-field pitting. This wood is attributed to Protophyllocladoxylon dolianitii Mussa 1958, and it is assumed to be of cordaitalean affinity, which is one of the dominant and arborescent element of the early Permian Gangamopteris Taiga. Evidence of growth patterns of the fossil wood, and the paleogeographical reconstruction shows that the host tree of the fossil wood was growing in a strongly seasonal polar light regime. The wide growth rings (5.315–12.316 mm) and the large number of tracheids per ring (99–288) indicate the tree flourished under favorable conditions during the growing season, with ample water and clement temperatures, enhanced by the extended daylight hours of the Antarctic-type summer. The occurrence of frost rings in the wood, corroborated by additional sedimentological information suggest that unusual climatic events (aperiodic cold and freezing events) occurred in terrestrial ecosystems of the southern Sydney Basin during the Kungurian. The study demonstrates that fossil wood of exceptional preservation, like the one reported here, can offer valuable and potentially unique information crucial for deep-time paleoclimatic reconstruction.

Post Gondwana breakup evolution of the SE Australia rifted margin revisited

AbstractLow‐temperature thermochronology (LTT) is commonly used to investigate onshore records of continental rifting and geomorphic evolution of passive continental margins. The SE Australian passive margin, like many others, has an elevated plateau separated from the coastal plain by an erosional escarpment, presumed to originate through Cretaceous rifting prior to Tasman Sea seafloor spreading. Previous LTT studies have focused on reconciling thermal histories with development of the present‐day topography. New apatite LTT data along an escarpment‐to‐coast transect define a classic “boomerang” (mean track length vs. fission‐track age), indicating variable overprinting of late‐Palaeozoic cooling ages by a younger, mid‐Cretaceous cooling event. Regionally, however, the boomerang trend diverges NNW away from the coast and crosses the escarpment, implying the underlying thermal history pre‐dates escarpment formation and is largely independent from post‐breakup landscape evolution. We suggest that Cretaceous cooling might relate to erosion of Permo‐Triassic sedimentary cover from a formerly more extensive Sydney Basin.

Stacked Parahaentzschelinia ichnofabrics from the Lower Permian of the southern Sydney Basin, southeastern Australia: Palaeoecologic and palaeoenvironmental significance

Trace fossils are sensitive indicators for environmental parameters (e.g., hydrodynamics, oxygen content, water depth, depositional rates, salinity), providing invaluable information to understand past depositional regimes not attainable from other sources of approaches. Here we report a new trace fossil assemblage dominated by a potential bivalve trace Parahaentzschelinia from the Lower Permian Snapper Point Formation, which records deposition in a storm-influenced delta front environment. Dense populations of Parahaentzschelinia occurred in two sections, forming stacked Parahaentzschelinia ichnofabrics and representing multiple burrow adjustments of a single trace maker (tellinid bivalve) subsequent to rapid sedimentation events caused by possible seasonal/annual runoffs. Statistical analysis of burrow lengths and numbers of adjustments suggests up to seven sequences of sediment accumulation events, supplying 3–13 cm thick clastic deposits at each time. A conservative sedimentation rate of 0.24 cm/year was estimated on the basis of two stacked Parahaentzschelinia ichnofabrics and the probable maximum lifespan of the modern tellinid genus. This rate is generally comparable to those derived from modern deltaic environments, lending further support to the interpretation that the ichnofabrics were formed in and characteristic of a deltaic setting. Our research highlights the utility of stacked equilibrium structures as a sensitive indicator of certain depositional regimes, and its applicability for assessing sedimentation rates as well as depositional conditions in the geological past.

Refined Permian–Triassic floristic timeline reveals early collapse and delayed recovery of south polar terrestrial ecosystems

AbstractThe collapse of late Permian (Lopingian) Gondwanan floras, characterized by the extinction of glossopterid gymnosperms, heralded the end of one of the most enduring and extensive biomes in Earth’s history. The Sydney Basin, Australia, hosts a near-continuous, age-constrained succession of high southern paleolatitude (∼65–75°S) terrestrial strata spanning the end-Permian extinction (EPE) interval. Sedimentological, stable carbon isotopic, palynological, and macrofloral data were collected from two cored coal-exploration wells and correlated. Six palynostratigraphic zones, supported by ordination analyses, were identified within the uppermost Permian to Lower Triassic succession, corresponding to discrete vegetation stages before, during, and after the EPE interval. Collapse of the glossopterid biome marked the onset of the terrestrial EPE and may have significantly predated the marine mass extinctions and conodont-defined Permian–Triassic Boundary. Apart from extinction of the dominant Permian plant taxa, the EPE was characterized by a reduction in primary productivity, and the immediate aftermath was marked by high abundances of opportunistic fungi, algae, and ferns. This transition is coeval with the onset of a gradual global decrease in δ13Corg and the primary extrusive phase of Siberian Traps Large Igneous Province magmatism. The dominant gymnosperm groups of the Gondwanan Mesozoic (peltasperms, conifers, and corystosperms) all appeared soon after the collapse but remained rare throughout the immediate post-EPE succession. Faltering recovery was due to a succession of rapid and severe climatic stressors until at least the late Early Triassic. Immediately prior to the Smithian–Spathian boundary (ca. 249 Ma), indices of increased weathering, thick redbeds, and abundant pleuromeian lycophytes likely signify marked climate change and intensification of the Gondwanan monsoon climate system. This is the first record of the Smithian–Spathian floral overturn event in high southern latitudes.

BRACHIOPOD ASSEMBLAGES OF THE EURYDESMA FAUNA IN GLACIAL- DEGLACIAL SEQUENCES FROM ARGENTINA AND AUSTRALIA

The Eurydesma Fauna characterizes the Late Pennsylvanian-Permian glacial-postglacial sediments recorded in several Gondwanan basins during the Late Paleozoic Ice Age (LPIA). Brachiopods, as one the most significant components of this fauna, are herein analyzed along with the associated bivalves, in two key sections from western and eastern Gondwana (Bonete Formation in the Sauce Grande Basin, eastern Argentina, and the Wasp Head Formation in the southern Sydney Basin, eastern Australia). The preliminary quantitative analysis indicates a high compositional similarity in both regions but occupancy exhibits important differences: brachiopod-dominated faunas can be found in eastern Australia (Tomiopsis and Trigonotreta are the most frequent taxa), and bivalve-dominated faunas are characteristic in eastern Argentina, where the brachiopods are poorly represented with the genera Tivertonia and Tomiopsis. In this locality, the development of r-strategy taxa, such as the bivalve Eurydesma, during the end of a glacial episode would adversely affect brachiopods’ abundance. This is also consistent with previous studies that indicate that brachiopods already showed a decrease in importance in Pennsylvanian communities from Argentina. Relative abundances of brachiopods and bivalves in both localities may reflect differences in the regional environmental conditions but, unfortunately, eastern Argentina lacks younger records to compare the faunal turnover with that of the Australian sequences. Despite the ecological structural differences identified (i.e. brachiopod:bivalve ratio), the postglacial Eurydesma fauna flourished in western and eastern Gondwana and it is striking that two faunas located on the opposite margins of this paleocontinent show such high compositional similarity during the development of a global postglacial event. This is particularly significant considering that the type of the basins (i.e. restricted vs open basins), biological features, paleoenvironmental conditions directly related to glacial dynamics, and also the diachronism of the transgression, can be controlling the composition of this fauna.

End-Permian (252 Mya) deforestation, wildfires and flooding—An ancient biotic crisis with lessons for the present

Current large-scale deforestation poses a threat to ecosystems globally, and imposes substantial and prolonged changes on the hydrological and carbon cycles. The tropical forests of the Amazon and Indonesia are currently undergoing deforestation with catastrophic ecological consequences but widespread deforestation events have occurred several times in Earth's history and these provide lessons for the future. The end-Permian mass-extinction event (EPE; ∼252 Ma) provides a global, deep-time analogue for modern deforestation and diversity loss. We undertook centimeter-resolution palynological, sedimentological, carbon stable-isotope and paleobotanical investigations of strata spanning the end-Permian event at the Frazer Beach and Snapper Point localities, in the Sydney Basin, Australia. We show that the typical Permian temperate, coal-forming, forest communities disappeared abruptly, followed by the accumulation of a 1-m-thick mudstone poor in organic matter that, in effect, represents a ‘dead zone’ hosting degraded wood fragments, charcoal and fungal spores. This signals a catastrophic scenario of vegetation die-off and extinction in southern high-latitude terrestrial settings. Lake systems, expressed by laterally extensive but generally less than a few-metres-thick laminated siltstones, generally lacking bioturbation, hosting assemblages of algal cysts and freshwater acritarchs, developed soon after the vegetation die-off. The first traces of vascular plant recovery occur ∼1.6 m above the extinction horizon. Based on analogies with modern deforestation, we propose that the global fungal and acritarch events of the Permo-Triassic transition resulted directly from inundation of basinal areas following water-table rise as a response to the abrupt disappearance of complex vegetation from the landscape. The δ13Corg values reveal a significant excursion toward low isotopic values, down to −31‰ (a shift of ∼4‰), across the end-Permian event. The magnitude of the shift at that time records a combination of changes in the global carbon cycle that were enhanced by the local increase in microbial activity, possibly also involving cyanobacterial proliferation. We envisage that elevated levels of organic and mineral nutrients delivered from inundated dead forests, enhanced weathering and erosion of extra-basinal areas, together with local contributions of volcanic ash, led to eutrophication and increased salinity of basinal lacustrine–lagoonal environments. We propose that the change in acritarch communities recorded globally in nearshore marine settings across the end-Permian event is to a great extent a consequence of the influx of freshwater algae and nutrients from the continents. Although this event coincides with the Siberian trap volcanic activity, we note that felsic–intermediate volcanism was extensively developed along the convergent Panthalassan margin of Pangea at that time and might also have contributed to environmental perturbations at the close of the Permian.

Estimation of the shear strength of fractured Gosford sandstone based on fractal theory and numerical modelling

The effects of joint roughness on the peak shear strength of fractured rock mass has been extensively investigated. Among these investigations, Barton's JRC-JCS model has been well recognized for its capability to characterize surface geometry. However, shear strength estimation is still a major challenge because of the difficulties involved in accurately calculating the joint roughness coefficient (JRC). Thus, alternative methods such as statistic methods based on fractal theory have been proposed to evaluate the impact of surface morphology on rock joints. Extensive evidences show that, the application of the fractal dimension alone cannot produce a satisfactory estimation of either the JRC or the peak shear strength. Therefore, this paper aims to investigate the peak shear strength of rock joints by adopting the fractal theory and via a numerical simulation. Gosford sandstone taken from Sydney Basin is adopted as the rock materials for both numerical validation and shear strength investigation. Along with numerical simulations on shear strength, a linear function has been proposed to describe the correlations among the root-mean-square of the first derivative of fracture profile (Z2), fractal dimension and the standard deviation. The peak shear strength is then accurately interpreted as a function of joint roughness indices: fractal dimension (D), standard deviation (SD) and Z2. Predictions by the proposed equation are compared with both the numerical simulation results and that reproduced by Barton's equation. Good agreement has been achieved even when the joint roughness coefficients (JRC) is varied which proves that the proposed equation is highly accurate and can be reused in other related applications.

Evaluation of Regional Air Quality Models over Sydney and Australia: Part 1—Meteorological Model Comparison

The ability of meteorological models to accurately characterise regional meteorology plays a crucial role in the performance of photochemical simulations of air pollution. As part of the research funded by the Australian government’s Department of the Environment Clean Air and Urban Landscape hub, this study set out to complete an intercomparison of air quality models over the Sydney region. This intercomparison would test existing modelling capabilities, identify any problems and provide the necessary validation of models in the region. The first component of the intercomparison study was to assess the ability of the models to reproduce meteorological observations, since it is a significant driver of air quality. To evaluate the meteorological component of these air quality modelling systems, seven different simulations based on varying configurations of inputs, integrations and physical parameterizations of two meteorological models (the Weather Research and Forecasting (WRF) and Conformal Cubic Atmospheric Model (CCAM)) were examined. The modelling was conducted for three periods coinciding with comprehensive air quality measurement campaigns (the Sydney Particle Studies (SPS) 1 and 2 and the Measurement of Urban, Marine and Biogenic Air (MUMBA)). The analysis focuses on meteorological variables (temperature, mixing ratio of water, wind (via wind speed and zonal wind components), precipitation and planetary boundary layer height), that are relevant to air quality. The surface meteorology simulations were evaluated against observations from seven Bureau of Meteorology (BoM) Automatic Weather Stations through composite diurnal plots, Taylor plots and paired mean bias plots. Simulated vertical profiles of temperature, mixing ratio of water and wind (via wind speed and zonal wind components) were assessed through comparison with radiosonde data from the Sydney Airport BoM site. The statistical comparisons with observations identified systematic overestimations of wind speeds that were more pronounced overnight. The temperature was well simulated, with biases generally between ±2 °C and the largest biases seen overnight (up to 4 °C). The models tend to have a drier lower atmosphere than observed, implying that better representations of soil moisture and surface moisture fluxes would improve the subsequent air quality simulations. On average the models captured local-scale meteorological features, like the sea breeze, which is a critical feature driving ozone formation in the Sydney Basin. The overall performance and model biases were generally within the recommended benchmark values (e.g., ±1 °C mean bias in temperature, ±1 g/kg mean bias of water vapour mixing ratio and ±1.5 m s−1 mean bias of wind speed) except at either end of the scale, where the bias tends to be larger. The model biases reported here are similar to those seen in other model intercomparisons.

Decoupling of nutrient cycles in a Eucalyptus woodland under elevated CO2

Abstract Elevated atmospheric [CO2] (eCO2) is currently altering nutrient cycling and availability in ecosystems worldwide. If the availabilities and turnover rates of macro‐ and micronutrients are differentially affected, then nutrient cycles may become out of sync (i.e., decoupled). We evaluated the impacts of 3 years of eCO2 (550 µmol CO2/mol) on the availability, stability and coupling of eleven essential macro and micronutrients in a mature, P‐limited Eucalyptus woodland from Eastern Australia (EucFACE). Despite increases in N and P availability in the first 18 months of study, nutrient availabilities and their stoichiometric ratios were unaffected by eCO2 across the study period (26–57 months of experimental duration). In contrast, the stability of nutrient availability increased under eCO2, which was concomitant with a reduction in the degree of biogeochemical coupling. Synthesis. We demonstrate that macro‐ and micro‐nutrient cycles can quickly become out of sync (i.e., decoupled) under eCO2 in a low‐nutrient Australian eucalypt woodland, despite the lack of consistent effects on nutrient availability; such decoupling of nutrient cycles may have unpredicted consequences in terms of ecosystem functioning under the widely assumed positive relationship between biogeochemical coupling and ecosystem functioning.

Residue and use‐wear analysis of non‐backed retouched artefacts from Deep Creek Shelter, Sydney Basin: Implications for the role of backed artefacts

ABSTRACTA previous use‐wear and residue analysis of backed artefacts from Deep Creek Shelter showed that they had a range of functions and had been used with a variety of raw materials. Were non‐backed retouched flakes at Deep Creek used for different purposes? To answer this question, 40 non‐backed specimens were selected for microscopic use‐wear and residue analysis. Not all of these non‐backed artefacts had been used, but we identified that many were scrapers, knives, incisors and saws. These tools were used for bone‐working and wood‐working, and possibly skin‐working and non‐woody plant‐processing. Some of these non‐backed retouched artefacts were hafted. For the first time, these results allow comparison of the tool use of backed and non‐backed artefacts in Australia. At Deep Creek, the range of functions for the non‐backed component was extremely similar to that of the backed artefacts. Although both artefact categories displayed similar tool use, they are distinguished in one interesting way: non‐backed specimens were often single purpose, dedicated to one function, whereas backed artefacts were often multifunctional and multipurpose. These results help us understand the structure of tool use in Australia.

Timing of Early and Middle Permian deglaciation of the southern hemisphere: Brachiopod-based 87Sr/86Sr calibration

Earth's transition from an icehouse to hothouse during the Late Paleozoic was characterized by a series of high paleolatitude glacial-interglacial events. However, the exact timing of these events remains unresolved. Here, we report on fifty-five calcitic shells of brachiopods and bivalves screened to obtain reliable 87Sr/86Sr ratios for Cisuralian (298.9-272.95 Ma) and Guadalupian (272.95-259.1 Ma) seawater. Specifically, we used well-preserved shells to build a 87Sr/86Sr seawater curve for the Sydney Basin, and then with the marine Look-up Table of the Permian calculated numerical ages of the stratigraphic succession. This allowed us to match seawater changes to the coeval P1 – P3 glacial-interglacial cycles recorded in the sedimentary successions of the Sydney Basin. Evaluation of the 87Sr/86Sr results revealed that onsets of the P2 and P3 glaciations in the Sydney Basin should be assigned to the early Artinskian and late Wordian, respectively. The range of 87Sr/86Sr values recorded by brachiopods from the Wandrawandian Siltstone coupled with recent geochronological dating of the Broughton Formation suggest that glacial phase P3 lasted about 2 Myr and was confined to the late Wordian – early Capitanian. Dating obtained using the Sr-isotope proxy from brachiopods agrees with the geochronologic ages, and they suggest that the glacial phases P1 to P3 became progressively shorter in duration and less intense. Conversely, the corresponding interglacials became progressively longer, and thus, documenting the gradual transition of the Permian icehouse to an ice-free greenhouse world. Our study confirms that strontium isotopes measured in screened brachiopod shell archives are sufficiently robust to date Paleozoic marine sedimentary successions, and are most valuable in sedimentary successions that otherwise lack geo-chronological dating.

Depositional environment, organic matter sources, and variable 17α(H)-diahopane distribution in Early Permian samples, southern Sydney Basin, Australia

Early Permian strata exposed in the southern part of the Sydney Basin, NSW, Australia, include the Pebbley Beach Formation, the Snapper Point Formation and the Wandrawandian Siltstone. These formations were deposited during the Late Paleozoic Ice Age, when Australia was close to the South Pole. The Pebbley Beach and Snapper Point formations were deposited in shallow marine to coastal environments, while the Wandrawandian Siltstone was deposited in deeper water following a marine transgression. However, opinions differ on the precise environmental and climatic conditions that prevailed during their deposition. Sixteen outcrop samples from these formations were collected and analysed to determine their depositional conditions and the source(s) of their organic matter.The biomarker and aromatic hydrocarbon distributions show that the rocks are in the early to mid-oil window. Some aromatic parameters show that the stratigraphically younger Wandrawandian Siltstone is more thermally mature than the older Pebbley Beach Formation, which is interpreted to be due to the geographic position of these outcrops in the Sydney Basin. The samples have low to intermediate pristane/phytane ratios (from 1.4 to 3.4), showing variation from oxic to suboxic depositional conditions. Most of the mudstones and siltstones sampled were deposited in a marine environment, with some fluvial-deltaic or estuarine influence, and contain mixed type II and type III organic matter. The Pebbley Beach formation is characterised by terpane distributions dominated by the C24 tetracyclic terpane, and to a lesser extent the C19 tricyclic terpane. The Snapper Point Formation has a mix of C19 and C23 tricyclic terpanes and C24 tetracyclic terpane, while the Wandrawandian Siltstone is dominated by C19, C21, and C23 tricyclic terpanes. The sterane distribution follows a C29 > C28 > C27 pattern in the majority of the samples, including in the marine deposited Wandrawandian Siltstone. The three formations have very variable relative amounts of diahopanes and other rearranged hopanes, with the highest C30*/C30 αβ hopane ratio (6.9) in the Wandrawandian Siltstone. This formation also has high amounts of diasteranes compared to the other two formations, but the relative amounts of diasteranes are not as high as for the diahopanes. Classically, this suggests a clay-rich sediment in an oxic or suboxic, acid-catalysed depositional environment, with enhanced diagenetic alteration of the biomarkers. The Wandrawandian Siltstone was deposited in suboxic conditions, not unusual to many rocks that contain much less rearranged hopanes. Unusual characteristics of the Wandrawandian Siltstone include significant slumping and soft sediment deformation, and deposition under periglacial-glacial conditions. The occurrence of the slumps on the continental slope led to significant sediment overturn, and this may have resulted in enhanced diagenetic and catalytic rearrangement reactions, leading to the elevated levels of diahopanes and other rearranged hopanes. The disequilibrium between the relative abundances of diahopanes and diasteranes suggests different formation mechanisms for these biomarkers.

Impact of aerosols of sea salt origin in a coastal basin: Sydney, Australia

Sea salt is one of the major aerosols in the atmosphere in both the fine and coarse size ranges. Newly formed sea salt particles have a similar composition to seawater; including elements such as Na, Cl, Mg, S, Ca, Br and K. However, once in the atmosphere sea salt particles can undergo chemical reactions with other airborne pollutants, resulting in a loss of chlorine (whereas Na is conservative). The modified aerosol is commonly referred to as aged sea spray or aged sea salt.Fine aerosols from two sites in the Sydney Basin were analysed for source fingerprints with components that may have originated from the ocean (i.e. fresh and aged sea spray). At Lucas Heights, 18.4 km from the nearest coast, the average source fingerprint concentrations of fresh and aged sea spray were 0.47 ± 0.02 and 1.08 ± 0.03 μg/m3, respectively. At Richmond, 58 km from the coast, the average fingerprint concentrations of fresh and aged sea spray were 0.26 ± 0.01 and 0.87 ± 0.02 μg/m3, respectively. At Lucas heights, fresh and aged sea spray contributed to 11% and 21% of PM2.5, respectively. At Richmond fresh and aged sea spray contributed to 4.8 ± 0.35 and 16 ± 0.5% of the PM2.5, respectively.The Cl/Na ratios of aged sea spray at Lucas Heights and Richmond were 0.72 and 0.87, respectively, in comparison to 1.54 for fresh sea salt. At Richmond the corresponding Ca/Na and K/Na ratios were both 0.037 (close to that of seawater), and at Lucas Heights, the corresponding ratios were 0.038 and 0.026, respectively.Back trajectory and Radon-222 analysis demonstrated that the largest concentrations of aged sea spray occur when the air masses had travelled over regions of anthropogenic sources. This confirms an interaction between anthropogenic precursors and sea spray that liberates chlorine enabling it to contribute to other chemical reactions in the atmosphere, e.g. resulting in an increase in the formation of ozone.

Stephen Gapps’ The Sydney Wars: Conflict in the Early Colony 1788-1817

Stephen Gapps’ The Sydney Wars covers the period of conflict in the Sydney Basin area between 1788 and 1817, detailing the various battles and massacres that took place in the early years of the Sydney colony. The book promotes itself as the first ‘detailed account’ of these conflicts in the Sydney area, and detailed it is. Gapps weaves together contemporary accounts from diaries, official dispatches to the British Empire, news reports and court testimony to present a thorough reckoning of the destruction dealt to lives and property across the three decades from first European contact. He paints a nuanced picture of the conflict which offers, in some respects, a dissenting voice in the narrative surrounding these frontier wars – a term Gapps himself takes some issue with.

Outcrop analysis and facies model of an Upper Permian tidally influenced fluvio-deltaic system: Northern Sydney Basin, SE Australia

AbstractAn integrated study of sedimentological, sequence-stratigraphic and palaeodispersal analysis was applied to the Upper-Permian clastic sedimentary succession in the Northern Sydney Basin, Australia. The succession is subdivided into fifteen facies and three facies associations. The facies associations are further subdivided into eight sub-facies associations. The sedimentary evolution involves progradation from delta-front to delta-plain to fluvial depositional environments, with a significant increase in sediment grain size across the unconformable contact that separates the deltaic from the overlying fluvial system. In contrast to the delta front that is wave/storm- and/or river-influenced, the delta plain is significantly affected by tides, with the impact of tidal currents decreasing up-sequence in the delta plain. The general lack of wave-influenced sedimentary structures suggests low wave energy in the delta plain. The abrupt termination of the tidal impact in the fluvial realm relates to the steep topographic gradients and high sediment supply, which accompanied the uplift of the New England Orogen. The sequence-stratigraphic framework includes highstand (deltaic forest and topset) and lowstand (fluvial topset) systems tracts, separated by a subaerial unconformity. In contrast to most of the mud-rich modern counterparts, this is an example of a sand-rich tidally influenced deltaic system, developed adjacent to the source region. This investigation presents a depositional model for tidal successions in regions of tectonic uplift and confinement.