As part of the $225 million Exploring for the Future programme, Geoscience Australia have undertaken an investigation into the resource potential of the Officer-Musgrave-Birrindudu region. Part of this project focusses on characterising palaeovalley groundwater resources within the West Musgrave region of Australia. This record presents a three-dimensional palaeovalley model and describes the method used in its generation. Understanding the 3D architecture of palaeovalleys is an important component of conceptualising the shallow groundwater system. In this region groundwater is the only significant water resource, and is critical for supporting local communities, industries and the environment. The data products released alongside this record are a base of gridded Cenozoic surface, a grid of the thickness of the Cenozoic and polygons defining the spatial extent of palaeovalleys. The study area encompasses the upper reaches of several large palaeovalleys. These valleys incised mostly crystalline rocks of the Musgrave Province and sedimentary rocks of the adjoining basin during the late Cretaceous. Subsequently, valleys were filled by Cenozoic-aged sediments, which now form the aquifers and aquitards of the modern-day groundwater system. Palaeovalley architecture has been shaped by a complex interplay of climatic, tectonic, and geological factors over geological time. In some cases, tectonic deformation has caused tilting or disruption of palaeovalleys with implications for groundwater flow. We modelled the base of Cenozoic surface across the project area and used this geological surface to identify palaeovalleys. The modelling process used airborne electromagnetic conductivity models, borehole data and geological outcrop as model inputs. Using these data, we interpreted the base of Cenozoic along AEM flightlines, at borehole locations and at the surface where Pre-Cenozoic geology was cropping out. These data were gridded to generate the base of Cenozoic surface. This surface was then used as the basis for interpreting palaeovalley extents. The resulting model is adequate for its purpose of better understanding the groundwater system. However, the model has considerable uncertainty due to uncertainty in the model inputs and data sparsity. The model performed much better within the centre of the project area within the Musgrave Province compared to the adjoining basins.

<div>This report brings together data and information relevant to understanding the regional geology, hydrogeology, and groundwater systems of the South Nicholson – Georgina (SNG) region in the Northern Territory and Queensland. This integrated, basin-scale hydrogeological assessment is part of Geoscience Australia’s National Groundwater Systems project in the Exploring for the Future program. While the northern Georgina Basin has been at the centre of recent investigations as part of studies into the underlying Beetaloo Sub-basin, no regional groundwater assessments have focused on central and southern parts of the Georgina Basin since the 1970s. Similarly, there has been no regional-scale hydrogeological investigation of the deeper South Nicholson Basin, although the paucity of groundwater data limited detailed assessment of the hydrogeology of this basin. This comprehensive desktop study has integrated numerous geoscience and hydrogeological datasets to develop a new whole-of-basin conceptualisation of groundwater flow systems and recharge and discharge processes within the regional unconfined aquifers of the Georgina Basin.</div><div><br></div><div>Key outputs arising from this study include: (1) the development of a hydrostratigraphic framework for the region, incorporating improved aquifer attribution for over 5,000 bores; and (2) publicly available basin-scale groundwater GIS data layers and maps, including a regional watertable map for the whole Georgina Basin. This regional assessment provides new insights into the hydrogeological characteristics and groundwater flow dynamics within the Georgina Basin, which can aid in the sustainable management of groundwater for current and future users reliant on this critical water resource.</div><div><br></div><div><br></div>

<div>AusAEM Western Resources Corridor Survey: Logistics Report, AEM Data, and GALEI conductivity estimates.</div><div><br></div><div>From&nbsp;May to October 2022, an airborne electromagnetic (AEM) survey was flown over parts of Western Australia, Northern Territory and South Australia. Geoscience Australia commissioned the survey in collaboration with the Geological Surveys of Western Australia (GSWA) and South Australia (GSSA)&nbsp;as part of the Australian Government's Exploring for the Future program and the Western Australian Government's Exploration Incentive Scheme.</div><div><br></div><div>A total of 58,858 line kilometres of new data were acquired. GA managed all aspects of the acquisition, quality control and processing of the AEM data.</div><div><br></div><div>The survey was flown by Xcalibur Aviation (Australia)&nbsp;Pty Ltd using its TEMPEST AEM system. The survey was flown in variable line directions and line spacings ranging from 20km to&nbsp;5km apart. Skytem Australia Pty Ltd also processed the data. This data package includes the acquisition and processing report, the final processed AEM data, and the results of the contractor's conductivity-depth estimates. The data package also contains the results and derived products from a 1D inversion by Geoscience Australia with its own inversion software.</div><div><br></div><div>Geoscience Australia's Exploring for the Future program provides pre-competitive information to inform decision-making by Government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. We are building a national picture of Australia's geology and resource potential by gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia's transition to a low emissions economy, strong resources and agriculture sectors, and economic opportunities and social benefits for Australia's regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight-year, $225m investment by the Australian Government.</div><div><br></div><div>The survey will become part of the national AusAEM airborne electromagnetic acquisition program, which aims to provide geophysical information to support investigations of the regional geology and groundwater system and better characterise the salinity, recharge and architecture of the aquifers within the upper few hundred metres of the subsurface. It will also provide data to allow for the study of trends in regolith thickness and variability, variations in bedrock conductivity, the conductivity of key bedrock (lithology-related) conductive units under cover; and (d) the groundwater systems of the region at a reconnaissance scale.</div>

<div><strong>Yathong, Forbes, Dubbo, and Coonabarabran Airborne Electromagnetic Survey Blocks.</strong></div><div><br></div><div>Geoscience Australia (GA), in collaboration with the Geological Survey of New South Wales (GNSW), conducted an airborne electromagnetic (AEM) survey from April to June 2023. The survey spanned from the north-eastern end of the Yathong-Ivanhoe Trough and extended across the Forbes, Dubbo, and Coonabarabran regions of New South Wales.&nbsp;A total of 15, 090-line kilometres of new AEM and magnetic geophysical data were acquired. This survey was entirely funded by&nbsp;GSNSW and GA managed acquisition, quality control, processing, modelling, and inversion of the AEM data.</div><div><br></div><div>The survey was flown by Xcalibur Aviation (Australia) Pty Ltd using a 6.25 Hz HELITEM® AEM system. The survey blocks were flown at 2500-metre nominal line spacings, with variations down to 100 metres in the Coonabarabran block. It was flown following East-West line directions. Xcalibur also processed the acquired data. This data package includes the acquisition and processing report, the final processed AEM data, and the results of the contractor's conductivity-depth estimates. The data package also contains the results and derived products from a 1D inversion by Geoscience Australia with its own inversion software.</div><div><br></div><div>The survey will be incorporated and become part of the national AusAEM airborne electromagnetic acquisition program, which aims to provide geophysical information to support investigations of the regional geology and groundwater.</div><div><br></div><div><strong>The data release package contains:</strong></div><div><br></div><div>1. A data release package <strong>summary PDF document</strong></div><div>2. The <strong>survey logistics and processing report</strong> and HELITEM® system specification files</div><div>3. <strong>Final processed point located line data</strong> in ASEG-GDF2 format for the five areas</div><div> -final processed dB/dt electromagnetic, magnetic and elevation data</div><div> -final processed B field electromagnetic, magnetic and elevation data</div><div><strong> <em>Conductivity estimates generated by Xcalibur’s inversion&nbsp;</em></strong></div><div> -point located conductivity-depth line data output from the inversion in ASEG-GDF2 format</div><div> -graphical (PDF) multiplot conductivity stacks and section profiles for each flight line</div><div> -graphical (PNG) conductivity sections for each line</div><div> -grids generated from the Xcalibur’s inversion in ER Mapper® format (layer conductivities slices, DTM, X & Z component for each of the 25 channels, time constants, TMI)</div><div>4.<strong> ESRI shape and KML</strong> (Google Earth) files for the flight lines and boundary</div><div>5<strong>. Conductivity estimates generated by Geoscience Australia's inversion&nbsp;</strong></div><div> -point located line data output from the inversion in ASEG-GDF2 format</div><div> -graphical (pdf) multiplot conductivity sections for each line</div><div> -georeferenced (PNG) conductivity sections (suitable for pseudo-3D display in a 2D GIS)</div><div> -GoCAD™ S-Grid 3D objects (suitable for various 3D packages)</div><div> -Curtain image conductivity sections in log & liner colour stretch (suitable 3D display in GA’s EarthSci)</div><div><br></div><div><strong>Directory structure</strong></div><div>├── <strong>01_Report</strong></div><div>├── <strong>02_XCalibur_delivered</strong></div><div>│&nbsp;&nbsp; ├── * survey_block_Name</div><div>│ ├── cdi</div><div>│ │ ├── sections</div><div>│ │ └── stacks</div><div>│ ├── grids</div><div>│ │ ├── cnd</div><div>│ │ ├── dtm</div><div>│ │ ├── emxbf</div><div>│ │ ├── emxdb</div><div>│ │ ├── emxff</div><div>│ │ ├── emxzbf</div><div>│ │ ├── emzdb</div><div>│ │ ├── time_constant</div><div>│ │ └── tmi</div><div>│ ├── located_data</div><div>│ ├── maps</div><div>│ └── waveform</div><div>│&nbsp;&nbsp; </div><div>├── <strong>03_Shape&kml</strong></div><div>└── <strong>04_GA_Layer_Earth_inversion</strong></div><div> ├── * survey_block_Name</div><div> ├── GA_georef_sections</div><div> │ ├── linear-stretch</div><div> │ └── log-stretch</div><div> ├── GA_Inverted_conductivity_models</div><div> ├── GA_multiplots</div><div> └── GA_sgrids</div><div> </div> <b>Final Processed point located line data is available on request from clientservices@ga.gov.au - Quote eCat# 149118</b>

<div>As part of the Exploring for the Future (EFTF) programme, the groundwater team undertook an in-depth investigation into characterising surface water -- groundwater interaction in the Cooper Creek floodplain using airborne electromagnetics (AEM). This work is to be released as part of the Lake Eyre Basin detailed inventory and as an EFTF extended abstract. As part of Geoscience Australia's commitment to transparent science, the scientific workflows that underpinned a large component of this investigation are to be released as a jupyter notebook. This notebook contains python code, figures and explanatory text that the reader can use to understand how the AEM data were processed, visualised, integrated with other data and interpreted.</div>

<div> Airborne electromagnetic (AEM) data has been acquired at 20km line spacing across much of the Australian continent and conductivity models generated by inverting these data are freely available. Despite the wide line spacing these data are suitable for imaging the near surface and better understanding groundwater systems. Twenty-kilometre spaced AEM data acquired over the Cooper Creek floodplain using a fixed-wing towed system were inverted using deterministic and probabilistic methods. The Cooper Creek is an anabranching ephemeral river system in arid eastern central Australia. We integrated conductivity data with a range of surface and subsurface data to characterise the hydrogeology of the region and infer groundwater salinity from the shallow alluvial aquifer across a more than 14,000 km2 Cooper Creek floodplain. The conductivity data also revealed several examples of focused recharge through a river channel forming a freshwater lens within the more regional shallow saline groundwater system.</div><div>&nbsp;</div><div>This work demonstrates that regional AEM conductivity data can be a valuable tool for understanding groundwater processes at various scales with implications for how to responsibly manage water resources. This work is especially important in the Australian context where high quality borehole data is typically sparse, but high-quality geophysical and satellite data are often accessible.</div><div> </div> This presentation was given to the 8th International Airborne Electromagnetics Workshop (AEM2023) (https://www.aseg.org.au/news/aem-2023)

<div>The Kati Thanda – Lake Eyre Basin (KT–LEB) covers about 1.2 million square kilometres of outback Australia. Although the basin is sparsely populated and relatively undeveloped it hosts nationally significant environmental and cultural heritage, including unique desert rivers, sweeping arid landscapes, and clusters of major artesian springs. The basin experiences climatic extremes that intermittently cycle between prolonged droughts and massive inland floods, with groundwater resources playing a critical role in supporting the many communities, industries, ecological systems, and thriving First Nations culture of the KT–LEB.</div><div><br></div><div>As part of Geoscience Australia’s National Groundwater Systems Project (in the Exploring for the Future Program) this report brings together contemporary data and information relevant to understanding the regional geology, hydrogeology and groundwater systems of Cenozoic rocks and sediments of the KT–LEB. This work represents the first whole-of-basin assessment into these vitally important shallow groundwater resources, which have previously received far less scientific attention than the deeper groundwater systems of the underlying Eromanga Basin (part of the Great Artesian Basin). The new knowledge and insights about the geology and hydrogeology of the basin generated by this study will benefit the many users of groundwater within the region and will help to improve sustainable management and use of groundwater resources across the KT–LEB.</div><div><br></div>

The product consists of 8,800 line kilometres of time‐domain airborne electromagnetic (AEM) geophysical data acquired over the far north part of South Australia known as the Musgrave Province. This product release includes: a) the measured AEM point located data, b) electrical conductivity depth images derived from the dataset, and c) the acquisition and processing report. The data were acquired using the airborne SkyTEM312 Dual Moment 275Hz/25Hz electromagnetic and magnetic system, which covered a survey area of ~14,000 km2, which includes the standard 1:250 000 map sheets of SG52-12 (Woodroffe), SG52-16 (Lindsay), SG53-09 (Alberga) and SG53-13 (Everard). The survey lines where oriented N-S and flown at 2km, 500m and 250m line spacing. A locality diagram for the survey is shown in Figure 1. This survey was funded by the Government of South Australia, as part of the Plan for Accelerating Exploration (PACE) Copper Initiative, through the Department of the Premier and Cabinet, (DPC) and the Goyder Institute of Water Research. Geoscience Australia managed the survey as part of a National Collaborative Framework project agreement with SA. The principal objective of this project was to capture a baseline geoscientific dataset to provide further information on the geological context and setting of the area for mineral systems as well as potential for groundwater resources, of the central part of the South Australian Musgrave Province. Geoscience Australia contracted SkyTEM (Australia) Pty. Ltd. to acquire SkyTEM312 electromagnetic data, between September and October 2016. The data were processed and inverted by SkyTEM using the AarhusInv inversion program (Auken et al., 2015) and the Aarhus Workbench Laterally Constrained Inversion (LCI) algorithm (Auken et al. 2005; Auken et al. 2002). The LCI code was run in multi-layer, smooth-model mode. In this mode the layer thicknesses are kept fixed and the data are inverted only for the resistivity of each layer. For this survey a 30 layer model was used. The thickness of the topmost layer was set to 2 m and the depth to the top of the bottommost (half-space) layer was set to 600 m. The layer thicknesses increase logarithmically with depth. The thicknesses and depths to the top of each layer are given in Table 1. The regional AEM survey data can be used to inform the distribution of cover sequences, and at a reconnaissance scale, trends in regolith thickness and variability, variations in bedrock conductivity, and conductivity values of key bedrock (lithology related) conductive units under cover. The data will also assist in assessing groundwater resource potential and the extent of palaeovalley systems known to exist in the Musgrave Province. A considerable area of the survey data has a small amplitude response due to resistive ground. It very soon becomes evident that lack of signal translates to erratic non-monotonic decays, quite opposite to the smooth transitional exponential decays that occur in conductive ground. Some sections of the data have been flown over what appears to be chargeable ground, hence contain what potentially can be identified as an Induced Polarization effect (airborne IP—AIP). For decades these decay sign changes, which characterize AIP, have not been accounted for in conventional AEM data processing and modelling (Viezzoli et al., 2017). Instead they have mostly been regarded as noise, calibration or levelling issues and are dealt with by smoothing, culling or applying DC shifts to the data. Not accounting for these effects is notable on the contractor’s conductivity-depth sections, where data can’t be modelled to fit the data hence large areas of blank-space have been used to substitute the conductivity structure. The selection of the survey area was undertaken through a consultative process involving the CSIRO, GOYDER Institute, Geological Survey of South Australia and the exploration companies currently active in the region (including industry survey partner PepinNini Minerals Ltd). The data will be available from Geoscience Australia’s web site free of charge. It will also be available through the South Australian Government’s SARIG website at https://map.sarig.sa.gov.au. The data will feed into the precompetitive exploration workflow developed and executed by the Geological Survey of South Australia (GSSA) and inform a new suite of value-added products directed at the exploration community.

<p>Airborne electromagnetic (AEM) data can be acquired cost-effectively, safely and efficiently over large swathes of land. Inversion of these data for subsurface electrical conductivity provides a regional geological framework for water resources management and minerals exploration down to depths of ~200 m, depending on the geology. However, for legacy reasons, it is not uncommon for multiple deterministic inversion models to exist, with differing details in the subsurface conductivity structure. This multiplicity presents a non-trivial problem for interpreters who wish to make geological sense of these models. In this article, we outline a Bayesian approach, in which various spatial locations were inverted in a probabilistic manner. The resulting probability of conductivity with depth was examined in conjunction with multiple existing deterministic inversion results. The deterministic inversion result that most closely followed the high-credibility regions of the Bayesian posterior probability was then selected for interpretation. Examining credibility with depth also allowed interpreters to examine the ability of the AEM data to resolve the subsurface conductivity structure and base geological interpretation on this knowledge of uncertainty. <p> <b>Citation:</b> Ray, A., Symington, N., Ley-Cooper, Y. and Brodie, R.C., 2020. A quantitative Bayesian approach for selecting a deterministic inversion model. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

<div>In response to the acquisition of national-scale airborne electromagnetic surveys and the development of a national depth estimates database, a new workflow has been established to interpret airborne electromagnetic conductivity sections. This workflow allows for high quantities of high quality interpretation-specific metadata to be attributed to each interpretation line or point. The conductivity sections are interpreted in 2D space, and are registered in 3D space using code developed at Geoscience Australia. This code also verifies stratigraphic unit information against the national Australian Stratigraphic Units Database, and extracts interpretation geometry and geological data, such as depth estimates compiled in the Estimates of Geological and Geophysical Surfaces database. Interpretations made using this workflow are spatially consistent and contain large amounts of useful stratigraphic unit information. These interpretations are made freely-accessible as 1) text files and 3D objects through an electronic catalogue, 2) as point data through a point database accessible via a data portal, and 3) available for 3D visualisation and interrogation through a 3D data portal. These precompetitive data support the construction of national 3D geological architecture models, including cover and basement surface models, and resource prospectivity models. These models are in turn used to inform academia, industry and governments on decision-making, land use, environmental management, hazard mapping, and resource exploration.</div>