A geophysical analysis of Aboriginal earth mounds in the Murray River Valley, South Australia

Earth mounds are common archaeological features in some regions of Australia, particularly within the Murray-Darling Basin. These features are generally considered to have formed via the repeated use of earth oven cookery methods employed by Aboriginal people during the mid- to late-Holocene. This study assesses the relative effectiveness of key geophysical methods including magnetometry, groundpenetrating radar (GPR) and electrical resistivity tomography (ERT) in mapping, and determining the stratigraphy of earth mound sites. Three earth mounds adjacent to Hunchee Creek, on Calperum Station in South Australia's Riverland region, were chosen to conduct a comparative trial of these methods. This research demonstrated that geophysics can be used to both locate mounds and provide information as to deposit thickness and size. Individual ovens within mounds can also be located. This suggests a greater potential role for geophysics in understanding the Holocene archaeological record in Australia.

3D mapping of the submerged Crowie barge using electrical resistivity tomography

This study explores the applicability and effectiveness of electrical resistivity tomography (ERT) as a tool for the high-resolution mapping of submerged and buried shipwrecks in 3D. This approach was trialled through modelling and field studies of Crowie, a paddle steamer barge which sunk at anchor in the Murray River at Morgan, South Australia, in the late 1950s. The mainly metallic structure of the ship is easily recognisable in the ERT data and was mapped in 3D both subaqueously and beneath the sedimentwater interface.The innovative and successful use of ERT in this case study demonstrates that 3D ERT can be used for the detailed mapping of submerged cultural material. It will be particularly useful where other geophysical and diver based mapping techniques may be inappropriate due to shallow water depths, poor visibility, or other constraints.

Regional risk assessment of acid sulfate soil acidification under climate change based on mechanistic modelling of pyrite oxidation during prolonged drought events

<p>Under changing climate conditions with expected higher risks on long periods of severe drought events, acid sulfate soils have a higher risk for acidification when exposed to oxygen under a falling water table. A regional or continental risk map for acidification under possible future climate scenarios is one of the tools for evaluating agricultural, economic and environmental impacts of acidification. The starting point is a simulation model with the relevant processes accounting for (i) the effect of changing meteorological boundary conditions on the water dynamics inside the soil and the ground water depth, (ii) diffusion of oxygen inside the soil profile, and (iii) kinetic dissolution of pyrite and geochemical alterations. The simulation tool HPx (Jacques et al., 2018) couples all these processes and enables to evaluation of different model structures. Numerical results were compared to an extreme drought event in the lower Murray River region, Murray-Darling Basin South Australia, between 2007 and 2010. A second step was the implementation of the mechanistic model in a spatial framework using python. As a proof of principle, we started with 5 x 5 km grid in areas with high probability of acid sulfate soils. Soil spatial data was pre-processed to determine model hydraulic parameters using pedotransfer functions. Climate and soil data were defined for each grid cell and formatted at run time for input into HPx. HPx simulations are controlled for the specific data for each grid cell. The final step is to perform the simulations on large spatial and temporal scales using supercomputing for which a linux-version of HP1 was developed. These developments open up new opportunities for coupled soil-climate modelling.</p> <p>Jacques, D., Simunek, J., Mallants, D. and van Genuchten, M.T. (2018). JOURNAL OF HYDROLOGY AND HYDROMECHANICS 66, 211-226</p>

Modelling effects of water regulation on the population viability of threatened amphibians

The regulation of river systems alters hydrodynamics and often reduces lateral connectivity between river channels and floodplains. For taxa such as frogs that rely on floodplain wetlands to complete their lifecycle, decreasing inundation frequency can reduce recruitment and increase the probability of local extinction. We virtually reconstructed the inundation patterns of wetlands under natural and regulated flow conditions and built stochastic population models to quantify the probability of local extinction under different inundation scenarios. Specifically, we explored the interplay of inundation frequency, habitat size, and successive dry years on the local extinction probability of the threatened southern bell frog Litoria raniformis in the Murray River floodplains of South Australia. We hypothesised that the changes in wetland inundation resulting from river regulation are driving the decline of L. raniformis in this system. Since river regulation began in the 1920s, the inundation frequency of many reliable breeding habitats has decreased to a point where they no longer support local populations. Increasing successive dry years drives the probability of local extinction, particularly in smaller wetlands. Larger wetlands and those with more frequent average inundation are less susceptible to these effects. Synthesis and Applications. Although the availability of suitable habitats has reduced, environmental water provision is a promising tool to mitigate the negative impacts of river regulation on amphibian populations. Our modelling approach can be used to prioritise the delivery of environmental water (through pumping or the operation of flow-regulating structures) to minimise the probability of local extinction in L. raniformis and potentially many other frog species. By quantifying the extinction risk of amphibian populations, we can strategically manage environmental water to reduce successive catastrophic breeding failures and increase the probability of persistence.

Murray River Societies in Australia through the Lens of Bioarchaeology

The Murray River Valley was one of the most densely occupied areas of inland Australia during the Holocene. Unlike other areas of Australia, the record of burials and human remains dominates archaeological narratives of this area’s Aboriginal experience. In this article, we review bioarchaeological evidence from the region. In addition to mortuary remains, also discussed in this article are evidence from human morphological variation, palaeopathology, and diet. While the valley is often treated as a single region, Aboriginal communities who lived along the Murray shared aspects of economic and cultural systems but also demonstrated diversity and local trajectories. Rather than a single grand narrative the valley’s bioarchaeological evidence shows variation which is the product of multiple local factors.