Murray Basin Research Articles

Cambro-Ordovician magmatism in the Delamerian orogeny: Implications for tectonic development of the southern Gondwanan margin

The Delamerian Orogen formed at the final stages of assembly of the Gondwana supercontinent. This system marks the initiation of subduction of the Pacific oceanic lithosphere along a prior rifted and extended passive margin. This paper explores the magmatic consequences following the early Cambrian initiation at the palaeo-Pacific margin in South Australia (SA) and western Victoria. Our data reveal a 50 Ma syn- to post-Delamerian tectono-magmatic history. Sampled from drill core from beneath the eastern Murray Basin cover in eastern SA, boninitic high Mg andesite from drill hole KTH12 and 516.1 ± 2 Ma quartz diorite suggest that first subduction established a volcanic arc within easternmost SA. Pacific-ward trench retreat then resulted in arc migration to reach the Mt Stavely Belt and Stawell Zones in western Victoria by ~510 Ma where boninitic arc magmatism continued until ~490 Ma. In the SA foreland of the Delamerian Orogen, early (522 ± 4 Ma) alkali basalt gave way to intrusion and extrusion of MORB-like tholeiites of back-arc basalt character.Through much of the middle and late Cambrian the SA Delamerian was in the back-arc and under extension but with periodic compression resulting from periodic Pacific-Australian plate coupling beneath the forearc in western Victoria.In SA syn-tectonic I- and S-type granites reflect interaction of MORB-like back-arc magmas and their transported heat with continental-derived sediment of the Kanmantoo Group. The termination of the Delamerian orogeny at ~490 Ma was accompanied by buoyancy-controlled, exhumation and erosion. This was driven by delamination of a mafic, crustal underplate, whose re-melting at 1.5 to 2 GPa and 1050 °C generated the unique 495 ± 1 Ma Kinchina/Monarto adakite. Delamination resulted in lithospheric mantle thinning and local convective overturn allowing upwelling of the asthenosphere to drive the post-kinematic magmatic phase of the Delamerian, yielding voluminous 490 Ma–470 Ma A-type granites.

Enhancing SWOT discharge assimilation through spatiotemporal correlations

The highly intermittent and sparse nature of the Surface Water and Ocean Topography (SWOT) river observations in both space and time poses a major challenge to users for most applications. While interpolation/assimilation efforts exist to assemble discrete SWOT river observations into a spatially complete and temporally continuous record, the efficacy of such efforts is severely compromised by large observation gaps. In this study, we introduced spatiotemporal error correlations in runoff fields into the Inverse Streamflow Routing (ISR) model to improve the gap-filling capability for creating continuous daily discharge. This enhanced ISR model was first investigated in the Ohio River basin, which showed very significant improvements with better reproduced spatial and temporal dynamics of the runoff fields and the discharge time series. Results using 25 validation gauges showed a more concentrated Kling-Gupta Efficiency distribution, where the median was improved from 0.494 to 0.750. The enhanced ISR model was further tested over 16 representative global river basins to verify the effectiveness and robustness of the proposed method. The best fitted e-fold correlation length and time leading to the greatest improvements varied largely among the 16 basins. While all basins benefitted from the spatiotemporal correlations in the SWOT gap-filling, basins suffering from poorer initial guess and fewer SWOT observations, such as the Dnieper, Kolyma and Murray basins, showed larger performance gains than others. Although the experiments were idealized and did not reflect all potential errors that may be present in a real-world application, we demonstrate that the utility of SWOT river products and their value in hydrologic sciences may be boosted by expanding a local/intermittent observation platform into a far-reaching source of hydrologic information through both river hydrodynamics in channel networks and spatiotemporal coherence of runoff errors.

South Australian geology and the State Heritage Register: an example of geoconservation of the Naracoorte Caves complex and karst environment

South Australia’s State Heritage Register contains 2294 listed places, the majority of which are from the ‘Built’ environment, ranging from settlers’ huts, community buildings, historical industrial sites to magnificent stone mansions. Only 96 places are linked to the ‘Natural’ environment. The Register listings protect heritage places from alteration, damage or removal without formal prior consultation, compulsory under the South Australian Development Act. ‘Natural’ environments are landscape-based and oriented towards Geological, Archaeological, Palaeontological and Speleological heritage (‘GAPS heritage’). A process to provide a greater balance between ‘Natural’ and ‘Built’ listings has initiated a series of State Heritage ‘Natural’ environment assessments, mostly of single sites. Two individual caves in the Naracoorte Caves National Park are already entered in the State Heritage Register as single sites. However, an innovative broader multiple-site nomination has focused on the many different but significant GAPS features contained within the 25 caves of the Naracoorte Caves National Park, providing a further level of protection for the land and the caves’ exteriors and interiors. The example of the Naracoorte Caves draws attention to the number of important land and coastal karst (limestone) features across South Australia that were generated by steady geological uplift of three large sections of Oligocene–Miocene limestone—the Nullarbor Plain, the Murray Basin and the Gambier Karstfield (which includes Naracoorte and Mount Gambier), resulting in specific karst forms worthy of a broader coordinating management approach across South Australian karst parks.

Phylogeography, classification and conservation of pink zieria (Zieria veronicea; Rutaceae): influence of changes in climate, geology and sea level in south-eastern Australia

We assessed genetic variation in the Australian shrub Zieria veronicea across its current distribution and used environmental niche modelling to predict its distribution at the Last Glacial Maximum (LGM). The species range, from Kangaroo Island in South Australia to northern Tasmania, includes substantial overland and marine disjunctions of up to ~ 500 km. By inferring historical patterns of connectivity and genetic differentiation from DNA sequences and AFLP data, we aimed to provide new insight into the history of the species-rich sclerophyll vegetation in south-eastern Australia. Genetic differentiation of populations was not correlated with the size of geographic disjunctions. The deepest genetic divergence was between populations on Kangaroo Island and the adjacent mainland, separated by a strait only 13 km wide. Populations in western Victoria and Tasmania, separated by the 300 km of Bass Strait, showed the lowest genetic differentiation. This pattern is consistent with dispersal of Z. veronicea into Tasmania, across the Bassian Plain, possibly as recently as the LGM, in line with inferred distribution at that time. Genetic patterns, soil ages and niche models support Quaternary colonisation of the lower Murray Basin, potentially from eastern South Australia. The history of a large (500 km) disjunction between populations in western and eastern Victoria is unclear; historical connectivity of populations through suitable habitats is assumed, but the timing and location of connections are not clear. Genetic data support the current recognition of two subspecies and their treatment as distinct entities under conservation legislation.

Restoring Murray River floodplain wetlands: Does the sediment record inform on watering regime?

AbstractThe floodplain wetlands of the southern Murray Darling Basin (MDB) have been subject to the impacts of catchment and water resource development for more than a century. Their current degraded state is attributed to the regulation of the rivers and abstraction of water volume for irrigation. The MDB Plan is to return at least 2,750 Gl of mean annual flow to the system to restore the condition of waterways. Considerable recent investment in infrastructure enables water to be released into the basin's floodplain wetlands. The proposed watering regime is underpinned by modelling that suggests that, before regulation, overbank flows would have occurred regularly as discharge peaked in winter and spring. Sediment cores have been extracted from over 50 floodplain wetlands of the southern Murray Basin. Those from several, large meander wavelength billabongs extend for 1,000–5,000 years suggesting that these sites were permanently inundated over that time. Others extend to ~200 years and are presumed not to have accumulated sediment until more recently. The records of most wetlands, however, only extend to the onset of river regulation in the 1920s, suggesting that before then they were not inundated for sufficient duration for net accumulation to occur. Preserved diatoms suggest that the shallow, plant‐dominated wetlands of the past have transitioned to deep, turbid water systems today. As rivers are identified as a source of sediment to wetlands, less regular inundation, rather than more, is a viable option in restoring the ecological function of these floodplain wetlands and in slowing sediment infill.

High-Grade Silica Sands in The Eastern Murray Basin NSW

Investigations in 1979 defined a sand resource at Wah Wah with three potential processing options to yield sand suitable for colourless glass making. In December 2016, further drilling was completed to infill some of the previously drilled area and extend into new areas. From this drilling, coloured and white sand resources have been defined, overlain by a clay unit. The sand has generally been considered to have a fluvial origin, but recent work suggests that the white sands may have a beach origin. White sand is defined by the 0.050% Fe2O3 contour and this resource coincides generally with higher yield, mostly underlying 6m to 8m of clay - the thinner overburden area. Estimated resources are 15 million tonnes of white sand with 0.035% Fe2O3 and 0.20% Al2O3 at a yield of 58% for 8.7 million tonnes of sand suitable for colourless glass making. Sand not suited to glass making can be used for other products. These resources are Indicated Resources for reporting under the JORC Code 2012. They are defined by drilling and testing, and found to be suited for glass and other uses. From the investigations, a number of processing techniques can be employed with the final decision dependant on user requirements. However, the 2016 work demonstrated that an attrition-gravity process will be suitable for colourless glass sand, and cheaper than the other options considered in 1979. Based on results, the sand appears to be suitable for other products, including filter media, various construction uses, and other applications depending on markets. Compared to the resource defined in 1979 this deposit is now expected to be suited to: - Selective extraction, - Reduced focus on a single market, - By-products to increase overall yield, - Lower cost processing for the higher value products, - Certainty that there is sufficient resource to meet longer term needs for a range of products.

Selective sulphidation of impurities in weathered ilmenite. Part 1 – Applicability to different ilmenite deposits and simulated Becher kiln conditions

A novel approach for the removal of chrome-bearing spinel impurities (chromite) from weathered ilmenite concentrates has been proposed. This involves a two-stage process where in Stage 1 the spinel impurities are subjected to selective surface sulphidation followed by physicochemical separation in Stage 2. In this Part 1 paper, the applicability of the selective sulphidation of spinel impurities at 1100 °C was investigated for different ilmenite concentrates sourced from the Murray Basin region in south-eastern Australia and from Bangka Island Indonesia. The results demonstrated that the selective sulphidation of the impurities can be applied to the Murray Basin ilmenites. This was indicated by the formation of sulphide-rich rims on the spinel impurities. The chrome spinels from the Indonesian ilmenite, however, were not sulphidised. This was most likely due to the refractory nature of the spinels as they contain higher concentrations of Mg and Al. The current study also simulated an industrial Becher kiln process in a laboratory roller-bed-furnace. The results show that the selective sulphidation conditions can be achieved using char and sulphur sources. It was also observed from these experiments that Mn impurities are also sulphidised. The current study also identified and presented the range of high temperature and gaseous conditions (pO2 and pS2) that promote the selective sulphidation of Mg, Mn, Sn and Y impurities.

Tortuosity estimate through paramagnetic gas diffusion in rock saturated with two fluids using T2 (z, t) low-field NMR

Petrophysical interpretation of 1H NMR relaxation responses from saturated rocks is complicated by paramagnetic species present in fluids. Oxygen dissolved in liquids is one common example. Dipolar interactions of oxygen’s unpaired electron spins with the magnetic moment of fluid nuclei provide a strong relaxation mechanism known as paramagnetic relaxation enhancement (PRE). As a result even low concentrations of dioxygen in its common triplet ground state significantly shorten longitudinal and transverse relaxation times of host fluids. This effect may be employed similarly to any standard tracer technique to study pore connectivity in porous media by detecting a change of oxygen concentration due to diffusion resolved in time and space. Since relaxation enhancement effect is likely stronger in non-wetting phase than in wetting one (where surface relaxation process dominates) this difference can be utilized to study wettability in immiscible multiphase systems. We use a relaxation time contrast between air-saturated and oxygen-free fluids to evaluate oxygen concentration change within two fluid phases saturating rock, to estimate time required to establish equilibrium concentration and to calculate a mutual diffusion coefficient of oxygen. A spatially- and time-resolved T2(z,t) experiment provides the time-dependent oxygen concentration change along the fully- and partially-saturated carbonate core plug exposed to air saturated oil at its inlet. We derive an effective mutual diffusion coefficient of oxygen and accordingly a tortuosity estimate as a function of position along the core and rock saturation. The spatially resolved oxygen diffusion-based tortuosity is compared to simulated conductivitybased tortuosity. The latter is calculated on a high-resolution micro-tomographic image of Mount Gambier limestone by solving the Laplace equation for conductivity.

Decoupling of solutes and water in regional groundwater systems: The Murray Basin, Australia

Documenting the origins, residence times, and movement of groundwater and the solutes that it contains is critical to understanding hydrogeological systems. This study uses Cl mass balance to determine the Cl accession time (i.e. the time required for Cl to accumulate) and 36Cl to estimate the residence times of Cl in the Victorian portion of the Murray Basin, southeast Australia. Much of the Murray Basin contains saline groundwater with total dissolved solids (TDS) concentrations commonly >14,000mg/L and locally up to 300,000mg/L. The total mass of Cl stored in the Victorian portion of the basin is estimated as between 12,400 and 47,100MT. Using present day rainfall totals and Cl concentrations in rainfall, the Cl accession time is 170 to 650ka. Aquifer thicknesses and groundwater salinity both increase westwards in this part of the Murray Basin. Consequently, the Cl accession times increase westward from 0.1–0.6ka to 286–1080ka. By contrast, 14C activities of the majority of the groundwater are >2pMC, and commonly much higher. Notwithstanding the difficulty in correcting 14C residence times, the widespread occurrence of groundwater with above background 14C activities implies that groundwater residence times are generally <30ka, which is substantially shorter than the Cl accession times. R36Cl (the ratio of 36Cl to total Cl×1015) values of the groundwater are between 20 and 230, and are uncorrelated with Cl concentrations. While it is difficult to determine precise Cl residence times, the observation that the R36Cl values are significantly higher than those that represent secular equilibrium with the aquifer matrix (R36Cl of 5 to 10) indicates that they are up to a few hundred thousand years and similar to the Cl accession times. The R36Cl values together with the geology of the aquifers, stable isotope ratios, and major ion geochemistry precludes halite dissolution, incorporation of connate water, or the long-term diffusion of Cl from clays as mechanisms of producing the elevated Cl concentrations. Rather, it is most likely that the high Cl concentrations result from recycling of solutes in saline lakes and playas or repeated cycles of evapotranspiration in the unsaturated zone.

Regional analysis techniques for integrating experimental and numerical measurements of transport properties of reservoir rocks

Assessing the mechanisms of micro-structural change and their effect on transport properties using digital core analysis requires balancing field of view and resolution. This typically leads to the compromise of working with relatively small samples, where boundary effects can be substantial. A direct comparison with experiment, as e.g. desirable to eliminate unknown parameters and integrate numerical and physical experiments, needs to consider these boundary effects. Here we develop a workflow to define measuring windows within a sample where these boundary effects are minimised allowing the integration of physical and numerical experiment. We consider in particular sleeve leakage and use a radial partitioning of the solutions to various transport equations to derive relevant regional measures, which may be used for the development of cross-correlations between physical properties.Samples of Bentheimer and Castlegate sandstone as well as Mt. Gambier limestone and a sucrosic dolomite are considered. The sample plugs are encased in rubber sleeves and micro-CT images acquired at ambient conditions. Using these high-resolution images we calculate transport properties, namely permeability and electrical conductivity, and analyse the resulting field solutions with regard to flux across different regions of interest. The latter are selected on the basis of distance to the sample sleeve inner surface. Clear bypassing at the sleeve-sample interface in terms of elevated fluxes is observed for all samples, although to different extent. We consider different sleeve boundary conditions to define a measuring window minimising these effects, use the procedure to compare flux averages defined over these measuring windows with conventional choices of simulation domains, and compare resulting physical cross-correlations.

Benchmarking passive seismic cover depth assessments

Passive seismic techniques utilise the properties of ambient seismic waves to infer information about the structure of the subsurface, namely the depth(s) at which significant impedance contrasts occur. Geoscience Australia has recently conducted three passive seismic surveys to assess the suitability of two passive seismic methods, the horizontal over vertical spectral ratio (HVSR) and spatial autocorrelation (SPAC) techniques, for estimating cover depth over crystalline basement. Both techniques rely on ambient seismic noise in the form of surface waves. The HVSR technique involves measurement of the horizontal and vertical components of ambient seismic noise at an individual site. Where an impedance contrast exists, a maximum is observed in the HVSR value at a frequency directly dependent on the interface depth. The SPAC technique utilises dispersion observed in surface waves, which is also dependent on interface depth. Shear wave subsurface velocity profiles are constructed through inversion of the HVSR and/or SPAC curves. The logistically simpler HVSR method, requiring only one seismometer, was found to produce estimates with significantly lower error than estimates from SPAC for depths up to 300 m in the Murray Basin, where unconsolidated to semi-consolidated Cenozoic sediments overly Paleozoic crystalline basement. Both HVSR and SPAC methods failed to resolve the target interface with the exception of one site in the Gawler Craton, located at a depth of 900m. Further work is planned for these data with different processing techniques. The HVSR technique produced estimates consistent with other geophysical techniques (airborne electromagnetic, refraction seismic, and magnetotelluric methods) for the majority of sites in the Thomson Orogen, where the Mesozoic Eromanga Basin, Cenozoic cover, and regolith associated with both these stratigraphic groups overly crystalline basement to a depth of up to 550 m. The accuracy of these profiles will be verified with stratigraphic drilling. Results from these three surveys provide strong support for the passive seismic technique, in particular the single station HVSR method, as a highly effective and logistically low-cost and simple tool suitable for mapping cover depth in many regions of interest across Australia.

An inter-disciplinary approach to airborne electromagnetics (AEM) survey design for groundwater exploration using the Australian Geoscience Data Cube and Morphotectonics

Over the past decade, advances in new satellite and airborne sensor technologies provide an opportunity for rapid multi-scale mapping, measurement and monitoring of the physical state of the crust, including resolution of key elements of surface and sub-surface hydrological systems. These advances have been mirrored by the development in advanced computational research infrastructure which is now giving the groundwater research community access to high-resolution (spatial and temporal) biophysical datasets (e.g. climate, ecology, geoscience and geospatial) relevant to broader hydrological systems understanding. This infrastructure facilitates integration of multiple datasets and rapid and improved signal processing, inversion, and sophisticated analysis. These datasets provide a catalyst for collaboration, with inter-disciplinary approaches enabling new discovery science in a 'big data' environment, and enabling the qualitative and quantitative analysis and modelling of landscape and hydrological system processes. In Australian landscapes, airborne electromagnetics (AEM) is widely used in near-surface (<200m) groundwater investigations due to the ability to acquire consistent, spatially coherent information of high quality using calibrated systems, in very short timeframes. This study reports on an evolving inter-disciplinary approach to AEM survey design for groundwater exploration. Recent investigations have employed time series analysis of surface water availability (using the Australian Geoscience Data Cube (AGDC)) combined with morphotectonic analysis of digital elevation datasets, tectonic analysis, and geomorphic analysis of satellite optical data, to help predict preferential recharge zones and shallow groundwater resources. This novel approach has been used successfully for groundwater exploration in the western Murray Basin and Kimberley Region of northern Australia.

Mapping cover-thickness to UNCOVER basement and deep Earth architecture and processes

Under the UNCOVER initiative it is generally accepted that construction of accurate cover-thickness maps is the most tractable and urgent means of facilitating resource exploration under cover. To meet this goal we have been undertaking benchmarking of various geophysical techniques, constructing a national database of Estimates of Geological and Geophysical Surfaces (EGGS) to store legacy estimates and developing machine learning algorithms to interpolate between these estimates. Benchmarking magnetic top estimates to ~700 drill sites across the Murray Basin highlights the importance of performing estimates using profile data as opposed to grids. Inversion of horizontal to vertical spectral ratio data, derived from single broadband seismometers, reveals surprisingly robust cover-thickness estimates. While these insights are directly relevant in supporting drilling programs they can also be used to constrain deep Earth architecture and processes. We show that inversion of basin subsidence data can be used to constrain lithospheric thickness and mapped chrono-stratigraphic surfaces can be used to test models of uplift of the Australian continent related to convective flow within the Earth’s mantle.

Geological and Exploration Models of Beach Placer Deposits, Integrated from Case-Studies of Southern Australia

The processes leading to the formation of beach placer deposits generally begin inland and terminate at the coast, including source rocks being weathered, eroded and then transported by streams and rivers to the coast, where the sediments are deposited in a variety of coastal environments. The coastal sediments are reworked by the action of waves, tides, longshore currents and wind, which are effective processes for sorting the mineral grains based on differences in their size and density, resulting in laminated or lens-shaped packages of sediments up to tens of meters thick that are rich in heavy minerals. Detailed studies of sedimentary basins, as well as peripheral (paleo-)valleys that drained sediment source areas, are important tools in the exploration for heavy mineral resources. Knowledge of the (paleo-)basin, associated valley architecture and the source of heavy minerals concentrated in the shorelines and valleys are useful guides to the potential for, and location of, economic deposits.Evidence from sedimentology can be combined with that from other geological and geophysical characteristics to arrive at a general reconstruction of basin and paleovalley architecture and depositional environments. Complex paleogeography of the shorelines can influence or determine the sites of heavy mineral concentration. Heavy mineral sands tend to concentrate in certain shoreline settings during storm activity. Repeated storm erosion and reworking over centuries (e.g., the southeastern coast of Australia) or millennia (e.g., the Eucla and Murray Basins of Australia) can progressively enrich heavy mineral sand deposits. Preservation of these deposits over a geological timeframe of millions of years can ensue through subsidence of coastal sediments, and during sea-level change that results in either shorelines migrating inland (marine transgression) or seaward (marine regression), potentially burying or stranding earlier deposits or reworking them to form younger deposits. Refinements in remote sensing and geophysical techniques, data processing, sedimentology and computer-aided interpretations provide effective, economic and efficient methods for modeling coastal reconstructions and for exploring provinces and terrains prospective for heavy mineral sand deposits. Landscape topography analysis, combined with geophysical methods that can resolve physical property contrasts between the shoreline sediments and underlying sequences, are increasingly used in mineral exploration to locate and to reconstruct paleoshorelines and paleovalleys.Australia has modern and ancient beach-placer deposits, both of which show many similar geologic features. The formation of these heavy mineral deposits provides one of the best examples of applying knowledge of modern systems (e.g., the west and east coasts of Australia) as an analogue to interpret and understand the geology and form of ancient deposits (e.g., the Eucla and Murray Basins of southern Australia). This study provides descriptive and exploration models of Australia’s heavy mineral sand deposits formed in coastal environments, which can be applied to similar settings worldwide.

WIM150 mineral sand deposit, Murray Basin, Australia: geology and mineral resources

The first significant heavy mineral sands discovery within the Murray Basin, Australia, was made in 1982 at the WIM150 deposit near Horsham, Victoria. This fine-grained (20–75 µm) deposit formed in an offshore environment (WIM-style deposit). The heavy minerals (HM) are within the Loxton Sand, which is prospective throughout the Murray Basin for HM in both strandlines and WIM-style deposits. At WIM150, HM are concentrated in a horizon that extends for 10 km north–south and 12 km east–west and has a thickness that ranges from 2 to 22 m with an average of 11.2 m. Measured, Indicated and Inferred Mineral Resources totalling 1650 million tonnes at 3.7% total HM were estimated in 2013. Test work has demonstrated that the resource can be processed to +20 µm and that the 20–38 µm size fraction contains significant concentrations of HM (14.8% of the HM within the 20–75 µm size fraction). Test work also demonstrated that the HM from the 20 to 38 µm size fraction contain more than 40% ZrO2 and CeO2 (assumed to be contained in zircon and monazite, respectively). The project is estimated to have an Ore Reserve mine life of 55 years and is the most advanced, in terms of development, of the Murray Basin WIM-style deposits. A definitive feasibility study for the WIM150 deposit was completed in mid-2013.

Regionalisation of freshwater fish assemblages in the Murray–Darling Basin, Australia

Regionalisations based on species assemblages are a useful framework for characterising ecological communities and revealing patterns in the environment. In the present study, multivariate analyses are used to discern large-scale patterns in fish assemblages in the Murray–Darling Basin, based on information from the Murray–Darling Basin Authority’s first Sustainable Rivers Audit (SRA), conducted in 2004–2007. The Basin is classified into nine regions with similar historical fish assemblages (i.e. without major human intervention), using data that combine expert opinion, museum collections and historical records. These regions are (1) Darling Basin Plains, (2) Northern Uplands, (3) Murray Basin Plains, (4) Northern Alps, (5) Central East, (6) Avoca Lowland, (7) Southern Slopes, (8) Southern Alps and (9) South-Western Slopes. Associations between assemblages and physical variables (catchment area, elevation, hydrology, precipitation, temperature) are identified and used to reinforce the definitions of regions. Sustainable Rivers Audit data are compared with the historical assemblages, highlighting species whose range and abundance have changed since the early 19th century. Notable changes include declines in native species such as silver perch, river blackfish, mountain galaxias, Macquarie perch, trout cod and freshwater catfish, and the advent of alien species including common carp, eastern gambusia, goldfish, redfin perch, brown trout and rainbow trout. Less significant declines are evident for native carp gudgeons, golden perch, two-spined blackfish, bony herring and flathead gudgeon. Changes are evident even in regions where habitats have been little disturbed in the past 200 years.

Micro-scale experimental investigation of the effect of flow rate on trapping in sandstone and carbonate rock samples

We present the results of a pore-scale experimental study of residual trapping in consolidated sandstone and carbonate rock samples under confining stress. We investigate how the changes in wetting phase flow rate impacts pore-scale distribution of fluids during imbibition in natural, water-wet porous media. We systematically study pore-scale trapping of the nonwetting phase as well as size and distribution of its disconnected globules. Seven sets of drainage-imbibition experiments were performed with brine and oil as the wetting and nonwetting phases, respectively. We utilized a two-phase miniature core-flooding apparatus integrated with an X-ray microtomography system to examine pore-scale fluid distributions in small Bentheimer sandstone (D = 4.9 mm and L = 13 mm) and Gambier limestone (D = 4.4 mm and L = 75 mm) core samples. The results show that with increase in capillary number, the residual oil saturation at the end of the imbibition reduces from 0.46 to 0.20 in Bemtheimer sandstone and from 0.46 to 0.28 in Gambier limestone. We use pore-scale displacement mechanisms, in-situ wettability characteristics, and pore size distribution information to explain the observed capillary desaturation trends. The reduction was believed to be caused by alteration of the order in which pore-scale displacements took place during imbibition. Furthermore, increase in capillary number produced significantly different pore-scale fluid distributions during imbibition. We explored the pore fluid occupancies and studied size and distribution of the trapped oil clusters during different imbibition experiments. The results clearly show that as the capillary number increases, imbibition produces smaller trapped oil globules. In other words, the volume of individual trapped oil globules decreased at higher brine flow rates. Finally, we observed that the pore space in the limestone sample was considerably altered through matrix dissolution at extremely high brine flow rates. This increased the sample porosity from 44% to 62% and permeability from 7.3 D to 80 D. Imbibition in the altered pore space produced lower residual oil saturation (from 0.28 to 0.22) and significantly different distribution of trapped oil globules.

The effect of changes in tool tip angle on the cutting performance of a pointed pick

ABSTRACT:Many types of mining machines use pointed style picks in the excavation of weak and medium strength rock ranging from coal and evaporates to shales and sandstones. This paper explores the effect of the initial onset of pick wear on changes in the cutting performance as reflected by an increase in pick tip angle at varying depths of cut using two different rock types. Rock cutting tests were performed in Gambier limestone and Gosford sandstone at depths ranging from 5 mm to 20 mm using a pointed pick having tip angles of 70°, 90° 100° and 110°. The results reveal an increase in tool angle has a more pronounced effect on normal force with a three to four-fold increase compared to less than a two-fold increase in cutting force. Forces and specific energy were also found to increase with depth of cut over the range of tip angles.

A review of the taxonomy and systematics of the echinoid genus Monostychia Laube, 1869

Sadler, T., Kroh, A. & Gallagher, S.J., March 2016. A review of the taxonomy and systematics of the echinoid genus Monostychia Laube, 1869. Alcheringa 40, xxx–xxx. ISSN 0311-5518A review of Monostychia, a stratigraphically important clypeasteroid echinoid genus in southern Australian Oligocene/Miocene strata, reveals uncertainty in relation to morphological features used in taxonomy. The result is that the exact systematic position of the genus remains unresolved at subfamily level. Monostychia and its type species, M. australis, are redescribed. Monostychia australis is restricted to the lower to middle Miocene Glenforslan Formation of the Murray Basin. Three other species currently within Monostychia, M. etheridgei, M. loveni and M. elongata, are discussed. Although it is concluded that M. etheridgei belongs in the genus and is a distinct species, the taxonomic position of M. loveni is questioned, and the validity of M. elongata as a separate species from M. australis remains uncertain. This work lays the foundation for further revisions of Monostychia with an expectation that such work will provide the basis for character determination that may be useful across other echinoid taxa.Tony Sadler [t.sadler@uq.edu.au] and Stephen J. Gallagher [sjgall@unimelb.edu.au], School of Earth Sciences, University of Melbourne, Victoria 3010, Australia; Andreas Kroh [andreas.kroh@nhm-wien.ac.at], Natural History Museum Vienna, Department of Geology and Palaeontology, Burging 7, 1010, Vienna, Austria.

Incongruent patterns of nuclear and chloroplast variation in Correa (Rutaceae): introgression and biogeography in south-eastern Australia

Correa (family Rutaceae) is a genus endemic to southern Australia, in which chloroplast introgression between species has previously been inferred. The current study aimed to document the extent of incongruence between molecular markers and taxonomy, describe patterns of geographic variation, and infer genetic and biogeographic processes important in the history of the genus. Sampling focused on subg. Correa (nine species) and included 166 samples from 95 localities. Samples were genotyped at the chloroplast loci trnL-trnF and trnK and the nuclear ITS regions, either by direct sequencing or by restriction digests of PCR products. Both chloroplast and ITS datasets resolved subg. Persistens (two species mostly from wet forests) as distinct from those of subg. Correa. Within subg. Correa chloroplast and ITS lineages were largely incongruent with each other and with current taxonomy, but both datasets showed similar geographic patterns. In each dataset there was one lineage mostly restricted to western South Australia and Western Australia, and one lineage widespread in eastern South Australia, Victoria, Tasmania, New South Wales and Queensland. The split between these geographic lineages occurs in South Australia, on the western side of the Murray basin; it is sharply defined in the chloroplast results, whereas the distributions of ITS lineages overlap. The geographic patterns and incongruence exhibited by both ITS and chloroplast markers provide evidence for substantial chloroplast and nuclear introgression between species. Geographic distributions of genetic lineages are consistent with divergence caused by a historical vicariance event across the lower Murray basin and subsequent reconnection of populations.