For more than half a century, seismic tomography has been used to map the volumetric structure of Earth’s interior, but only recent advances in computation have enabled the application of this technique at scale. Estimates of surface waves that travel between two seismic stations can be reconstructed from a stack of cross-correlations of continuous data recorded by seismometers. Here, we use data from the Exploring for the Future program AusArray deployment to extract this ambient noise signal of Rayleigh waves and use it to image mid- to upper-crustal structure between Tennant Creek and Mount Isa. Our aim was to establish a repeatable, semi-automatic workflow that can be extended to the entire Australian continent and beyond. Shear wave velocity models at 4, 6, 8 and 10 s periods are presented. A strong low-velocity anomaly (2.5 km/s) at a period of 4 s (~2–4 km depth) delineates the outline of the newly discovered, and prospective for hydrocarbons, Carrara Sub-basin. A near-vertical high-velocity anomaly (3.5 km/s) north of Mount Isa extends from the near surface down to ~12 km and merges with northeast-trending anomalies. These elongate features are likely to reflect compositional variations within the mid-crust associated with major structures inferred to be associated with base metal deposits. These outcomes demonstrate the utility of the ambient noise tomography method of imaging first-order features, which feed into resource potential assessments. <b>Citation: </b>Hejrani, B., Hassan, R., Gorbatov, A., Sambridge, M. Hawkins, R., Valentine, A., Czarnota, K. and Zhao, J., 2020. Ambient noise tomography of Australia: application to AusArray deployment. 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. <b>See eCat record <a href="https://dx.doi.org/10.26186/148676">#148676</a> for the updated version of the model package.</b>

The ‘Australia’s Future Energy Resources’ (AFER) project is a four-year multidisciplinary investigation of the potential energy commodity resources in selected onshore sedimentary basins. The resource assessment component of the project incorporates a series of stacked sedimentary basins in the greater Pedirka-western Eromanga region in eastern central Australia. Using newly reprocessed seismic data and applying spatially enabled, exploration play-based mapping tools, a suite of energy commodity resources have been assessed for their relative prospectivity. One important aspects of this study has been the expansion of the hydrocarbon resource assessment work flow to include the evaluation of geological storage of carbon dioxide (GSC) opportunities. This form of resource assessment is likely to be applied as a template for future exploration and resource development, since the storage of greenhouse gases has become paramount in achieving the net-zero emissions target. It is anticipated that the AFER project will be able to highlight future exploration opportunities that match the requirement to place the Australian economy firmly on the path of decarbonisation.

The South Nicholson Basin and immediate surrounding region are situated between the Paleo- to Mesoproterozoic Mount Isa Province and McArthur Basin. Both the Mount Isa Province and the McArthur Basin are well studied; both regions host major base metal mineral deposits, and contain units prospective for hydrocarbons. In contrast, the South Nicholson Basin contains rocks that are mostly undercover, for which the basin evolution and resource potential are not well understood. To address this knowledge gap, the L210 South Nicholson Seismic Survey was acquired in 2017 in the region between the southern McArthur Basin and the western Mount Isa Province, crossing the South Nicholson Basin and Murphy Province. The primary aim of the survey was to investigate areas with low measured gravity responses (‘gravity lows’) in the region to determine whether they represent thick basin sequences, as is the case for the nearby Beetaloo Sub-basin. Key outcomes of the seismic acquisition and interpretation include (1) expanded extent of the South Nicholson Basin; (2) identification of the Carrara Sub-basin, a new basin element that coincides with a gravity low; (3) linkage between prospective stratigraphy of the Isa Superbasin (Lawn Hill Formation and Riversleigh Siltstone) and the Carrara Sub-basin; and (4) extension of the interpreted extent of the Mount Isa Province into the Northern Territory. <b>Citation:</b> Carr, L.K., Southby, C., Henson, P., Anderson, J.R., Costelloe, R., Jarrett, A.J.M., Carson, C.J., MacFarlane, S.K., Gorton, J., Hutton, L., Troup, A., Williams, B., Khider, K., Bailey, A.H.E. and Fomin, T., 2020. South Nicholson Basin seismic interpretation. 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.

The AusAEM1 survey is the world’s largest airborne electromagnetic survey flown to date, extending across an area exceeding 1.1 million km2 over Queensland and the Northern Territory. Approximately 60 000 line kilometres of data were acquired at a nominal line spacing of 20 km. Using this dataset, we interpreted the depth to chronostratigraphic surfaces, assembled stratigraphic relationship information, and delineated structural and electrically conductive features. Our results improved understanding of upper-crustal geology, led to 3D mapping of palaeovalleys, prompted further investigation of electrical conductors and their relationship to structural features and mineralisation, and helped us continuously connect correlative outcropping units separated by up to hundreds of kilometres. Our interpretation is designed to improve targeting and outcomes for mineral, energy and groundwater exploration, and contributes to our understanding of the chronostratigraphic, structural and upper-crustal evolution of northern Australia. More than 150 000 regional depth measurements, each attributed with detailed geological information, are an important step towards a national geological framework, and offer a regional context for more detailed, smaller-scale AEM surveys. <b>Citation:</b> Wong, S.C.T., Roach, I.C., Nicoll, M.G., English, P.M., Bonnardot, M.-A., Brodie, R.C., Rollet, N. and Ley-Cooper, A.Y., 2020. Interpretation of the AusAEM1: insights from the world’s largest airborne electromagnetic survey. 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.

A key challenge in exploring Australian onshore sedimentary basins is limited seismic data coverage. Consequently, well logs are often the main datasets that can be used to understand the subsurface geology. The primary aim of this study was to develop a methodology for visualising the three-dimensional (3D) tectonostratigraphic architecture of sedimentary basins using well data, which can then be used to quickly screen areas warranting more detailed studies of resource potential. This project has developed a workflow that generates 3D well correlations using sequence stratigraphic well tops to visualise the regional structural and stratigraphic architecture of the Amadeus, Canning, Officer and Georgina basins in the Centralian Superbasin. Thirteen Neoproterozoic‒Paleozoic supersequence tops were interpreted in 134 wells. Three-dimensional well correlations provide an effective regional visualisation of the tectonostratigraphic architecture across the main depocentres. This study redefines the Centralian Superbasin as encompassing all western, northern and central Australian basins that had episodically interconnected depositional systems driven by regional subsidence during one or more regional tectonic events between the Neoproterozoic and middle Carboniferous. The Centralian Superbasin began to form during Neoproterozoic extension, and underwent several phases of partial or complete disconnection and subsequent reconnection of depositional systems during various regional tectonic events before final separation of depocentres at the culmination of the Alice Springs Orogeny. Regional 3D correlation diagrams have been generated to show the spatial distribution of these supersequences, which can be used to visualise the distribution of stratigraphic elements associated with petroleum, mineral and groundwater systems. <b>Citation: </b>Bradshaw, B., Khider, K., MacFarlane, S., Rollet, N., Carr, L. and Henson, P., 2020. Tectonostratigraphic evolution of the Centralian Superbasin (Australia) revealed by three-dimensional well correlations. 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> A key issue for explorers in Australia is the abundant sedimentary and regolith cover obscuring access to underlying potentially prospective rocks. &nbsp;Multilayered chronostratigraphic interpretation of regional broad line-spaced (~20&nbsp;km) airborne electromagnetic (AEM) conductivity sections have led to breakthroughs in Australia’s near-surface geoscience. &nbsp;A dedicated/systematic workflow has been developed to characterise the thickness of cover and the depth to basement rocks, by delineating contact geometries, and by capturing stratigraphic units, their ages and relationships. &nbsp;Results provide a fundamental geological framework, currently covering 27% of the Australian continent, or approximately 2,085,000&nbsp;km2. &nbsp;Delivery as precompetitive data in various non-proprietary formats and on various platforms ensures that these interpretations represent an enduring and meaningful contribution to academia, government and industry.&nbsp;The outputs support resource exploration, hazard mapping, environmental management, and uncertainty attribution.&nbsp;This work encourages exploration investment, can reduce exploration risks and costs, helps expand search area whilst aiding target identification, and allows users to make well-informed decisions. Presented herein are some key findings from interpretations in potentially prospective, yet in some cases, underexplored regions from around Australia.&nbsp;</div> This abstract was submitted & presented to the 8th International Airborne Electromagnetics Workshop (AEM2023) (https://www.aseg.org.au/news/aem-2023)

The AusAEM1 airborne electromagnetic survey extends across an area exceeding 1.1 million km2 over Queensland and the Northern Territory. Approximately 60,000 line kilometres of data were acquired at a nominal line spacing of 20 km (Ley-Cooper et al., 2020). To improve targeting and outcomes for mineral, energy and groundwater exploration, we conducted a regional interpretation of this dataset to characterise the subsurface geology of northern Australia. The interpretation includes the depth to chronostratigraphic surfaces, compilation of stratigraphic relationship information, and delineation of structural and electrically conductive features. In addition to help connecting correlative outcropping units separated by up to hundreds of kilometres, the results led to 3D mapping of palaeovalleys and prompted further investigation of electrical conductors and their relationship to structural features and mineralisation. Approximately 200,000 regional depth point measurements, each attributed with detailed geological information, are an important step towards a national geological framework, and offer a regional context for more detailed, smaller-scale AEM surveys. Refer to Wong et al., (2020) for more details on the AusAEM1 interpretation.

Effective mineral, energy and groundwater resource management and exploration rely on accurate geological maps. While geological maps of the surface exist and increase in resolution, maps of the subsurface are sparse, and the underpinning geological and geophysical constraints are disordered or non-existent. The Estimates of Geological and Geophysical Surfaces (EGGS) database seeks to enable robust subsurface geological mapping by establishing an ordered collection of precious geological and geophysical interpretations of the subsurface. EGGS stores the depth to geological boundaries derived from boreholes as well as interpretations of depth to magnetic top assessments, airborne electromagnetics inversions and reflection seismic profiles. Since geological interpretation is iterative, links to geophysical datasets and processing streams used to image the subsurface are stored. These metadata allow interpretations to be readily associated with the datasets from which they are derived and re-examined. The geological basis for the interpretation is also recorded. Stratigraphic consistency is maintained by linking each interpretation to the Australian Stratigraphic Units Database. As part of the Exploring for the Future program, >170 000 points were entered into the EGGS database. These points underpin construction of cover thickness models and economic fairway assessments. <b>Citation:</b> Mathews, E.J., Czarnota, K., Meixner, A.J., Bonnardot, M.-A., Curtis, C., Wilford, J., Nicoll, M.G., Wong, S.C.T., Thorose, M. and Ley-Cooper, Y., 2020. Putting all your EGGS in one basket: the Estimates of Geological and Geophysical Surfaces database. 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.

To meet the increasing demand for natural resources globally, industry faces the challenge of exploring new frontier areas that lie deeper undercover. Here, we present an approach to, and initial results of, modelling the depth of four key chronostratigraphic packages that obscure or host mineral, energy and groundwater resources. Our models are underpinned by the compilation and integration of ~200 000 estimates of the depth of these interfaces. Estimates are derived from interpretations of newly acquired airborne electromagnetic and seismic reflection data, along with boreholes, surface and solid geology, and depth to magnetic source investigations. Our curated estimates are stored in a consistent subsurface data repository. We use interpolation and machine learning algorithms to predict the distribution of these four packages away from the control points. Specifically, we focus on modelling the distribution of the base of Cenozoic-, Mesozoic-, Paleozoic- and Neoproterozoic-age stratigraphic units across an area of ~1.5 million km2 spanning the Queensland and Northern Territory border. Our repeatable and updatable approach to mapping these surfaces, together with the underlying datasets and resulting models, provides a semi-national geometric framework for resource assessment and exploration. <b>Citation:</b> Bonnardot, M.-A., Wilford, J., Rollet, N., Moushall, B., Czarnota, K., Wong, S.C.T. and Nicoll, M.G., 2020. Mapping the cover in northern Australia: towards a unified national 3D geological 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.

The Mesoproterozoic South Nicholson Basin sits between, and overlies, the Paleoproterozoic Mount Isa Province to the east and the southern McArthur Basin to the northwest. The McArthur Basin and Mount Isa Province are well studied and highly prospective for both mineral and energy resources. In contrast, rocks in the South Nicholson region (incorporating the Mount Isa Province, the Lawn Hill Platform and the South Nicholson Basin, and geographically straddling the Northern Territory and Queensland border) are mostly undercover, little studied and consequently relatively poorly understood. A comprehensive U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon and xenotime geochronology program was undertaken to better understand the stratigraphy of the South Nicholson region and its relationship to the adjacent, more overtly prospective Mount Isa Province and McArthur Basin. The age data indicate that South Nicholson Basin deposition commenced ca. 1483 Ma, with cessation at least by ca. 1266 Ma. The latter age, based on U-Pb xenotime, is interpreted as the timing of postdiagenetic regional fluid flow. The geochronology presented here provides the first direct age data confirming that the South Nicholson Group is broadly contemporaneous with the Roper Group of the McArthur Basin. Some rocks, mapped previously as Mesoproterozoic South Nicholson Group and comprising proximal, immature lithofacies, have detrital spectra consistent with that of the late Paleoproterozoic McNamara Group of the western Mount Isa Province; this will necessitate a revision of existing regional stratigraphic relationships. The stratigraphic revisions and correlations proposed here significantly expand the extent of highly prospective late Paleoproterozoic stratigraphy across the South Nicholson region, which, possibly, extends even further west beneath the Georgina and Carpentaria basins. Our data and conclusions allow improved regional stratigraphic correlations between Proterozoic basins, improved commodity prospectivity and targeted exploration strategies across northern Australia. <b>Citation:</b> Carson, C.J., Kositcin, N., Anderson, J.R., Cross, A. and Henson, P.A., 2020. New U–Pb geochronology for the South Nicholson region and implications for stratigraphic correlations.. 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.