The Exploring for the Future Program facilitated the acquisition of major geoscience datasets in northern Australia, where rocks are mostly under cover and the basin evolution, mineral, energy and groundwater resource potential are, in places, poorly constrained. In an effort to support sustainable, regional economic development and build stronger communities in these frontier areas, integration of new and legacy data within a consistent platform could enhance the recognition of cross-disciplinary synergies in sub-surface resource investigations. Here we present a case study in the South-Nicholson Basin, located in a poorly exposed area between the prospective Mt Isa Province and the McArthur Basin. Both regions host major base metal deposits, contain units prospective for energy resources, and hold significant groundwater resources in the overlying Georgina Basin. In this study, we interpret a subset of new regional-scale data, which include ~1 900 km of deep seismic reflection data and 60 000 line kilometres of AusAEM1 airborne electromagnetic survey, supplemented with legacy information. This interpretation refines a semi-continental geological framework, as input to national coverage databases and informs decision-making for exploration and groundwater resource management. This study provides a 3D chronostratigraphic cover model down to the Paleoproterozoic basement. We mapped the depth to the base of intervals corresponding to geological eras, as well as deeper pre-Neoproterozoic superbasin boundaries to refine the cover model. The depth estimates, based on the compilation, interpretation and integration of geological and geophysical datasets, inform the basement architecture controls on evolution of the basin, with several key outcomes: 1) expanded mapped size of the South Nicholson Basin, potentially, increasing prospectivity for hydrocarbons and basin-hosted mineralisation, 2) improved stratigraphic unit correlations across the region, 3) identification of major crustal structures, some of which are associated with mineralisation and springs, and 4) improved basin architecture definition, supporting future investigation of groundwater resources.

The Mesoproterozoic Roper Group of the McArthur Basin has excellent petroleum potential but exploration has been hampered by poor constraints on its post-depositional history that has compromised understanding of the tectonostratigraphic evolution of the basin. The Derim Derim Dolerite occupies an important position in the event chronology of the McArthur Basin, having intruded the Roper Group prior to post-Roper basin inversion, and it is also a major component of Mesoproterozoic intraplate mafic magmatism in northern Australia. Since 1997, the Derim Derim Dolerite has been assigned a magmatic crystallisation age of 1324 ± 4 Ma (all uncertainties are 95% confidence), based on unpublished Sensitive High Resolution Ion Micro Probe (SHRIMP) U–Pb analyses on baddeleyite attributed to a dolerite sample from Bureau of Mineral Resources drill-hole Urapunga 5. Herein, we establish that the SHRIMP sample originated from the type locality of the Derim Derim Dolerite in outcrop 90 km northwest of Urapunga 5 and document the 207Pb/206Pb date interpreted from the 1997 dataset. New U–Pb SHRIMP reanalysis of the same grain-mounts yielded a mean 207Pb/206Pb date of 1320.1 ± 5.3 Ma, confirming the 1997 result, and Isotope Dilution-Thermal Ionisation Mass Spectrometry (ID TIMS) analysis of baddeleyites plucked from the mounts yielded a precise mean 207Pb/206Pb date of 1327.5 ± 0.6 Ma. This date is significantly older than a baddeleyite U–Pb ID-TIMS date of ca 1313 Ma recently reported elsewhere from dolerite in the Beetaloo Sub-basin 200 km to the south, indicating that magmatism attributed to the Derim Derim Dolerite spanned at least 10–15 Ma. Previously documented geochemical variation in Mesoproterozoic intraplate mafic rocks across the Northern Territory (such as the 1325 ± 36 Ma Galiwinku Dolerite in the McArthur Basin, 1316 ± 40 Ma phonolites in the Nimbuwah Domain of the eastern Pine Creek Orogen, and 1295 ± 14 Ma gabbro in the Tomkinson Province) may reflect episodic pulses of magmatism hitherto obscured by the low precision of the available isotopic dates. The timing and geochemistry of Derim Derim-Galiwinku mafic igneous activity is strikingly similar to that of the Yanliao Large Igneous Province (LIP) in the northern North China Craton, and the global paucity of 1330–1300 Ma LIPs suggests that the North Australian Craton and the North China Craton were in relatively close proximity at that time.

Exploring for the Future (EFTF) is a four-year $100.5 million initiative by the Australian Government conducted by Geoscience Australia in partnership with state and Northern Territory government agencies, CSIRO and universities to provide new geoscientific datasets for frontier regions. As part of this program, Geoscience Australia acquired two new seismic surveys that collectively extend across the South Nicholson Basin (L120 South Nicholson seismic line) and into the Beetaloo Sub-basin of the McArthur Basin (L212 Barkly seismic line). Interpretation of the seismic has resulted in the discovery of new basins that both contain a significant section of presumed Proterozoic strata. Integration of the seismic results with petroleum and mineral systems geochemistry, structural analyses, geochronology, rock properties and a petroleum systems model has expanded the knowledge of the region for energy and mineral resources exploration. These datasets are available through Geoscience Australia’s newly developed Data Discovery Portal, an online platform delivering digital geoscientific information, including seismic locations and cross-section images, and field site and well-based sample data. Specifically for the EFTF Energy project, a petroleum systems framework with supporting organic geochemical data has been built to access source rock, crude oil and natural gas datasets via interactive maps, graphs and analytical tools that enable the user to gain a better and faster understanding of a basin’s petroleum prospectivity. <b>Citation:</b> Henson Paul, Robinson David, Carr Lidena, Edwards Dianne S., MacFarlane Susannah K., Jarrett Amber J. M., Bailey Adam H. E. (2020) Exploring for the Future—a new oil and gas frontier in northern Australia. <i>The APPEA Journal</i><b> 60</b>, 703-711. https://doi.org/10.1071/AJ19080

The petroleum systems summary report provides a compilation of the current understanding of petroleum systems for the McArthur Basin, including the prospective Beetaloo Sub-basin. The contents of this report are also available via the Geoscience Australia Portal at https://portal.ga.gov.au/, called The Petroleum Systems Summary Assessment Tool (Edwards et al., 2020). Three summaries have been developed as part of the Exploring for the Future (EFTF) program (Czarnota et al., 2020); the McArthur Basin, the Canning Basin, and a combined summary of the South Nicholson Basin and Isa Superbasin region. The petroleum systems summary reports aim to facilitate exploration by summarising key datasets related to conventional and unconventional hydrocarbon exploration, enabling a quick, high-level assessment the hydrocarbon prospectivity of the region.

<div>This report presents new data from X-ray Computerised Tomography (XCT) scanning, gas porosity and permeability testing, and grain density measurements of 79 of 82 samples from the Birrindudu and McArthur basins. Three plugs could not be recovered from the whole core section. Plugs were taken from depths of interest from drill holes Manbulloo S1, Hidden Valley S2, Broughton 1, ANT003, 99VRNTGSDD1, 99VRNTGSDD2, Lamont Pass 3 and WLMB001B.</div><div><br></div><div>These tests were performed in 2023 by CSIRO in Perth. The full results as provided by CSIRO to Geoscience Australia are provided as an attachment to this document.&nbsp;This work was conducted as part of the Exploring for the Future Program (Officer–Musgrave–Birrindudu module).</div><div><br></div>

<p>Northern Australia contains extensive Proterozoic-aged sedimentary basins with potential energy, mineral, and groundwater resources concealed beneath the surface. The region is remote and largely underexplored with limited data and infrastructure and therefore is considered to have high exploration risk. Exploration for hydrocarbons and basin-hosted base metals, although perceived to have very different exploration models, share a number of important similarities and key parameters. Foremost amongst these is shale geochemistry since the same reduced, organic-rich shales are both a hydrocarbon source rock and a depositional site for base metal mineralisation. Furthermore, anoxic and euxinic (anoxic with free hydrogen sulfide, H2S) water column and sediments are important for both the preservation of organic matter and as a H2S reservoir needed for precipitation of ore minerals after reaction with oxic metalliferous brines. Here we present new organic and inorganic geochemical datasets for shales in the South Nicholson Basin, Lawn Hill Platform and greater McArthur Basin, including the organic-richness of shales and the inorganic geochemistry of redox-sensitive trace metals, to demonstrate changes in water-column chemistry and favourable base metals depositional sites. Parameters such as total organic carbon (TOC) content and redox-sensitive elemental concentrations are used to identify prospective packages with hydrocarbon and base metals mineral resource potential <p>The results reveal many units in the Lawn Hill Platform, South Nicholson Basin and greater McArthur Basin contain organic-rich rocks. A cut-off value of TOC ≥ 2 wt% is used to define several shale and carbonate sequences in the region that are favourable for both hydrocarbon generation and as base metals depositional sites. Inorganic geochemistry results demonstrate a range of paleoredox conditions, from predominantly anoxic, ferruginous conditions with deviations, to sub-oxic and euxinic conditions. Future work mapping the temporal and spatial distribution of this geochemistry, in combination with other mappable geological criteria, is required to create mineral and petroleum systems models that can define prospective fairways across the basins and increase our understanding of resource potential. <p>The precompetitive data generated in this study highlight the utility of shared geochemical datasets for resource exploration in the region. More broadly, this study improves our understanding of the energy and mineral potential across northern Australia, supporting resource decision-making and investment.

Discovery of mid-Proterozoic (1.8 – 0.8 billion years ago, Ga) indigenous biomarkers is a challenge, since biologically informative molecules of such antiquity are commonly destroyed by metamorphism or overprinted by drilling fluids and other anthropogenic petroleum products. The previously oldest biomarkers were reported from the 1.64 Ga Barney Creek Formation in the McArthur Basin, northern Australian. In this study, we present the discovery of clearly indigenous biomarker molecules from carbonaceous shales of the 1.73 Ga Wollogorang Formation in the southern McArthur Basin, extending the biomarker record back in time by ~90 million years. The extracted hydrocarbons illustrate typical mid-Proterozoic signatures with a large unresolved complex mixture, high methyl-alkane/n-alkane ratios and absence of eukaryotic steranes. Also below detection limits were acyclic isoprenoids, saturated carotenoid derivatives, bacterial hopanes and aromatic hopanoids and steroids. Detected, however, were continuous homologous series (C13-C22) of 2,3,4- and 2,3,6-trimethyl aryl isoprenoids (AI). These breakdown products of aromatic carotenoids are the oldest known biogenic molecules, revealing the activity of phototrophic green (Chlorobiaceae) and purple sulphur bacteria (Chromatiaceae). The compounds provide evidence for at least temporary, very shallow (less than ~20 m) stratification of the McArthur Basin 1.73 Ga ago, supporting models of pervasive anoxic conditions in mid-Proterozoic basins.

NDI Carrara 1 is a deep stratigraphic well completed in 2020 as part of the MinEx CRC National Drilling Initiative (NDI), in collaboration with Geoscience Australia and the Northern Territory Geological Survey. It is the first stratigraphic test of the Carrara Sub-Basin, a newly discovered depocentre in the South Nicholson region. The well intersected Proterozoic sediments with numerous hydrocarbon shows, likely to be of particular interest due to affinities with the known Proterozoic plays of the Beetaloo Sub-basin and the Lawn Hill Platform, including two organic-rich black shales and a thick sequence of interbedded black shales and silty-sandstones. Alongside an extensive suite of wireline logs, continuous core was recovered from 283.9 m to total depth at 1750.8 m, providing high-quality data to support comprehensive analysis. Presently, this includes geochronology, geochemistry, geomechanics, and petrophysics. Rock Eval pyrolysis data demonstrates the potential for several thick black shales to be a source of hydrocarbons for conventional and unconventional plays. Integration of these data with geomechanical properties highlights potential brittle zones within the fine-grained intervals where hydraulic stimulation is likely to enhance permeability, identifying prospective Carrara Sub-basin shale gas intervals. Detailed wireline log analysis further supports a high potential for unconventional shale resources. Interpretation of the L210 and L212 seismic surveys suggests that the intersected sequences are laterally extensive and continuous throughout the Carrara Sub-basin, potentially forming a significant new hydrocarbon province and continuing the Proterozoic shale play fairway across the Northern Territory and northwest Queensland. This abstract was submitted and presented at the 2022 Australian Petroleum Production and Exploration Association (APPEA), Brisbane (https://appea.eventsair.com/appea-2022/)

The ca. 1.4 Ga Roper Group of the greater McArthur Basin in northern Australia comprises the sedimentary fill of one of the most extensive Precambrian hydrocarbon-bearing basins preserved in the geological record. It is interpreted to have been deposited in a large epeiric sea known as the Roper Seaway. Trace element data suggest that the redox structure of the basin was a shallow oxic layer overlying deeper suboxic to anoxic waters along with a prominent episode of euxinia. These anoxic and sulfidic conditions, as inferred by redox sensitive trace element (TE) abundances, (molybdenum, vanadium and uranium), developed due to high organic carbon loading consistent with models that suggest that euxinic conditions cannot develop until the flux of organic matter is significantly greater than the flux of bioavailable iron (Fe³⁺), which permits sulphate reduction to proceed. Considering the high reactive iron and molybdenum contents of these shales and the requirement for S/Fe ratios >2 for euxinia to develop, suggest sufficient atmospheric O₂ was available for oxidative scavenging of S and Mo from the continents. This is further supported by prominent negative cerium anomalies within these shales, indicative of active oxidative redox cycling of cerium. We propose that the high organic matter flux was the result of increased nutrient loading to the Roper Seaway from weathering of the continental hinterland. Data from both major and high-field strength elements (niobium, tantalum, zirconium and, hafnium) together with neodymium isotopes (¹⁴³Nd/¹⁴⁴Nd) indicate that a likely mechanism for this enhanced nutrient delivery was a shift in sedimentary provenance to a more primitive (i.e. mafic) precursor lithology. This switch in provenance would have increased phosphorus delivery to the Roper Seaway, contributing to high primary productivity and the onset of euxinia. This dataset and model serve as a basis for understanding the temporal evolution of the deepest sections of the Roper Seaway and finer scale changes in the environment at this time. <b>Citation:</b> Grant M. Cox, Amber Jarrett, Dianne Edwards, Peter W. Crockford, Galen P. Halverson, Alan S. Collins, André Poirier, Zheng-Xiang Li, Basin redox and primary productivity within the Mesoproterozoic Roper Seaway, <i>Chemical Geology</i>, Volume 440, 2016, Pages 101-114, ISSN 0009-2541, https://doi.org/10.1016/j.chemgeo.2016.06.025.

<p>The Mesoproterozoic Roper Group of the McArthur Basin has excellent petroleum potential, but its poorly constrained post-depositional history has hampered resource exploration and management. The Derim Derim Dolerite occupies an important position in the regional event chronology, having intruded the Roper Group prior to deformation associated with the ‘Post-Roper Inversion’ event. It was assigned a magmatic crystallisation age of 1324 ± 4 Ma (uncertainties are 95% confidence unless otherwise indicated) in 1997, based on unpublished Sensitive High Resolution Ion Micro Probe (SHRIMP) U-Pb analyses of dolerite-hosted baddeleyite from sample 97106010, collected from the Derim Derim Dolerite type locality in outcrop within the northwestern McArthur Basin. Herein, we refine these data via Isotope Dilution-Thermal Ionisation Mass Spectrometry (ID-TIMS) analysis of baddeleyites plucked from the SHRIMP grain-mounts, which yielded a precise mean 207Pb/206Pb date of 1327.5 ± 0.6 Ma. This date is significantly older than a baddeleyite U-Pb ID-TIMS date of 1313.8 ± 1.3 Ma recently obtained from dolerite ALT-05, sampled in Pacific Oil and Gas Ltd drillhole Altree 2, near the northern margin of the Beetaloo Sub-basin, and 200 km south of 97106010. This pair of results indicates that Derim Derim Dolerite magmatism spanned at least 10-15 Ma. Previously documented geochemical variation in Mesoproterozoic mafic rocks across the Northern Territory (such as the 1325 ± 36 Ma (2σ) Galiwinku Dolerite in the northern McArthur Basin, 1316 ± 40 Ma phonolites intruding the eastern Pine Creek Orogen, and 1295 ± 14 Ma gabbro in the Tomkinson Province) may reflect episodic pulses of magmatism hitherto obscured by the low precision of the available isotopic dates. <p><b>Citation:</b> Bodorkos, S., Yang, B., Collins, A.S., Crowley, J., Denyszyn, S.W., Claoue-Long, J.C., Anderson, J.R. and Magee, C., 2020 Precise U–Pb baddeleyite dating of the Derim Derim Dolerite: evidence for episodic mafic magmatism in the greater McArthur Basin. 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.