part-page article on stratigraphic issues

The Browse Basin, NW Australia, contains significant hydrocarbon reserves. It was identified as potentially suitable for offshore geological storage of CO2. A sequence stratigraphic analysis of 60 key wells was conducted to improve the understanding of sequence architecture, facies and palaeogeographic evolution of the earliest Campanian to latest Maastrichtian section for CO2 storage assessment.in the Browse Basin. This study provided new insights into sediment source and transport to the basin deep. Well log analysis and seismic interpretation identified submarine fans of the K60 interval as potential CO2 storage targets. In some areas potential lateral connection between submarine fans and the shelf via submarine canyons and channels can limit containment. More detailed investigations at a prospect scale are needed to fully assess sand-body connectivity and CO2 storage potential.

The advent of Chemical Abrasion-Isotope Dilution Thermal Ionisation Mass Spectrometry (CA-IDTIMS) has revolutionised U-Pb dating of zircon, and the enhanced precision of eruption ages determined on volcanic layers within basin successions permits an improved calibration of biostratigraphic schemes to the numerical timescale. The Guadalupian and Lopingian (Permian) successions in the Sydney, Gunnedah, Bowen and Canning basins are mostly non-marine and include numerous airfall tuff units, many of which contain zircon. The eastern Australian palynostratigraphic scheme provides the basis for much of the local correlation, but the present calibration of this scheme against the numerical timescale depends on a correlation to Western Australia, using rare ammonoids and conodonts in that succession to link to the standard global marine biostratigraphic scheme. High-precision U¿Pb zircon dating of tuff layers via CA-IDTIMS allows this tenuous correlation to be circumvented¿the resulting direct calibration of the palynostratigraphy to the numerical timescale highlights significant inaccuracies in the previous indirect correlation. The new data show: the top of the Praecolpatites sinuosus (APP3.2) Zone lies in the early Roadian, not the middle Kungurian; the top of the Microbaculispora villosa (APP3.3) Zone lies in the middle Roadian, not the early Roadian; the top of the Dulhuntyispora granulata (APP4.1) Zone lies in the Wordian, not in the latest Roadian; the top of the Didecitriletes ericianus (APP4.2) Zone lies in the first half of the Wuchiapingian, not the latest Wordian; the Dulhuntyispora dulhuntyi (APP4.3) Zone is exceptionally short and lies within the Wuchiapingian, not the early Capitanian; and the top of the Dulhuntyispora parvithola (APP5) Zone lies at or near the Permo-Triassic boundary, not in the latest Wuchiapingian.

Discussion of available stratigraphic resources: the Australian Stratigraphic Units Database (ASUD); documentation of procedures for modifying existing units or establishing new ones; contact details for the Australian Stratigraphy Commission members and ASUD staff. Suggestions on ways of raising awareness through modern media such as a podcast or app, and a request for feedback on what sort of approach might appeal to a university student audience.

The upper Permian to Lower Triassic sedimentary succession in the southern Bonaparte Basin represents an extensive marginal marine depositional system that hosts several gas accumulations. Of these, the Blacktip gas field has been in production since 2009, while additional identified gas resources are under consideration for development. The sedimentary succession extends across the Permian–Triassic stratigraphic boundary, and shows a change in lithofacies changes from the carbonate dominated Dombey Formation to the siliciclastic dominated Tern and Penguin formations. The timing, duration, distribution and depositional environments of these formations in the Petrel Sub-basin and Londonderry High is the focus of this study. The sedimentary succession extending from the Dombey to the Penguin formations is interpreted to represent marginal marine facies which accumulated during a long-lasting marine transgression that extended over previous coastal and alluvial plain sediments of the Cape Hay Formation. The overlying Mairmull Formation represents the transition fully to marine deposition in the Early Triassic. Regional scale well correlations and an assessment of available biostratigraphic data suggest marginal marine deposition systems were initiated outboard before the End Permian Extinction event, subsequently migrated inboard at about the Permian–Triassic stratigraphic boundary, and continued to be deposited through the faunal and floral recovery phase as Triassic species became established. The depositional history of the basin is translated to a chronostratigraphic framework which has implications for predicting the character and distribution of petroleum system elements in the Petrel Sub-basin and Londonderry High. Appeared in The APPEA Journal 61(2) 699-706, 2 July 2021

This report presents palynological data compiled and analysed as part of Geoscience Australia’s ‘Assessing the Status of Groundwater in the Great Artesian Basin’ project, commissioned by the Australian Government through the National Water Infrastructure Fund – Expansion. Diverse historic nomenclature within the Great Artesian Basin (GAB) Jurassic‒Cretaceous succession in different parts of the GAB makes it difficult to map consistently GAB resources across borders, at a basin-wide scale, in order to provide a geological and hydrogeological framework to underpin effective long-term management of GAB water resources. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, examined 706 wells across the GAB and compiled 407 wells, having Jurassic‒Cretaceous succession, with reviewed palynology data (down to total depth). This initial palynology data review allowed identification of new data samples from 20 wells (within the 407 wells) in Queensland and South Australia to fill data and knowledge gaps within the Jurassic‒Cretaceous GAB succession. This study resulted in: 1) a summary compilation of existing palynology data on 407 wells selected to create a regional framework between the Surat, eastern Eromanga and western Eromanga basins, to help regional correlations across the GAB, 2) a review of several different palynology zonation schemes and adaptation to a single consistent scheme, applying the scheme of Price (1997) for the spore pollen zonation and Partridge (2006) for the marine zonation, 3) updated stratigraphic charts across the Surat, Eromanga and Carpentaria basins, 4) identification of data and knowledge gaps, and 5) sampling of new palynology data to help fill some data and knowledge gaps identified in 13 key wells in the Surat Basin and 10 key wells in the Eromanga Basin. In the Surat Basin the new sampling program has targeted units within: the Evergreen Formation, Hutton Sandstone, Springbok Sandstone, Gubberamunda Sandstone, Orallo Formation, Mooga Sandstone, Bungil Formation. In the Eromanga Basin the sampling program targeted units within: the Poolowanna Formation, Hutton Sandstone, Adori Sandstone, Algebuckina Sandstone, Namur Sandstone and Hooray Sandstone. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, provides updated biostratigraphic information compiled in a standardised chronostratigraphic framework across the Surat, Eromanga and Carpentaria basins that mostly comprise the GAB. This work allows comparison of various geological, lithological, hydrogeological schemes. It provides links between various lithostratigraphic units, with different nomenclature, across jurisdictions. It also links these units to some key regional chronostratigraphic markers that can be used to generate consistent surfaces that correlate to aquifer and aquitard boundaries. The compilation of legacy and newly sampled and analysed palynology data allows refinement of a regional chronostratigraphic framework that can be used to map a common Mesozoic play interval scheme across all the resource types, for basin-scale assessments of groundwater, hydrocarbons, carbon capture and storage, and mineral potential. From this correlation of time equivalent geological units deposited in different environments, it is then possible to map internal lithological variations in stratigraphic facies within sequences that influence hydraulic properties and connectivity within and between aquifers across the GAB. The updated geometry and variability mapping within and between aquifers will help refine the conceptual hydrogeological model, to assess how aquifers and aquitards are connected within the GAB. The revised conceptual hydrogeological model can facilitate an improved understanding of potential impacts from exploitation of sub-surface resources in the basin, providing a basis for more robust water balance estimates.

Discussion of the uses made of the Australian Stratigraphic units database (ASUD), the sources of data to update it, and issues with maintaining quality. The importance of correct and consistent terminology, and the value of good reviews and editing are highlighted with examples.

Geoscience Australia has undertaken a regional seismic mapping study that extends into the frontier deep-water region of the offshore Otway Basin. This work builds on seismic mapping and petroleum systems modelling published in the 2021 Otway Basin Regional Study. Seismic interpretation spans over 18 000 line-km of new and reprocessed data collected in the 2020 Otway Basin seismic program and over 40 000 line-km of legacy 2D seismic data. Fault mapping has resulted in refinement and reinterpretation of regional structural elements, particularly in the deep-water areas. Structure surfaces and isochron maps highlight Shipwreck (Turonian–Santonian) and Sherbrook (Campanian–Maastrichtian) supersequence depocentres across the deep-water part of the basin. These observations will inform the characterisation of petroleum systems within the Upper Cretaceous succession, especially in the underexplored deep-water region. Presented at the 2022 Australian Petroleum Production & Exploration Association (APPEA)

This Bonaparte Basin dataset contains descriptive attribute information for the areas bounded by the relevant spatial groundwater feature in the associated Hydrogeology Index map. Descriptive topics are grouped into the following themes: Location and administration; Demographics; Physical geography; Surface water; Geology; Hydrogeology; Groundwater; Groundwater management and use; Environment; Land use and industry types; and Scientific stimulus. The Bonaparte Basin is a large sedimentary basin off the north-west coast of Australia, encompassing both offshore and onshore areas. It has undergone multiple phases of extension, deposition, and tectonic inversion from the Paleozoic to Cenozoic periods. The Petrel Sub-basin, situated on the eastern margin, exhibits a north-west trending graben/syncline and exposes lower Paleozoic rocks onshore while transitioning to upper Paleozoic, Mesozoic, and Cenozoic sediments offshore. Onshore, the basin's geological structures reflect two dominant regimes: north to north-north-east trending Proterozoic basement structures associated with the Halls Creek Mobile Zone, and north-north-west trending basin structures linked to the rifting and later compressional reactivation of the Petrel Sub-basin. The Petrel Sub-basin has experienced growth and tectonic inversion since the Paleozoic, marked by volcanic activity, deposition of clastics and carbonates, and extension events. During the Devonian, extension occurred along faults in the Ningbing Range, leading to the deposition of clastics and carbonates. The Carboniferous to Permian period witnessed offshore extension associated with the Westralian Superbasin initiation, while onshore deposition continued in shallow marine and transitional environments. Thermal subsidence diminished in the Early Permian, and subsequent compression in the mid-Triassic to Early Jurassic reactivated faults, resulting in inversion anticlines and monoclines. After the Early Jurassic, the sub-basin experienced slow sag with predominantly offshore deposition. Post-Cretaceous deformation caused subsidence, and an Early Cretaceous transgression led to shallow marine conditions and the deposition of chert, claystone, and mudstones. Mid-Miocene to Recent compression, related to continental collision, reactivated faults and caused localized flexure. The stratigraphy of the onshore Bonaparte Basin is divided into Cambro-Ordovician and Middle Devonian to Early Permian sections. Studies have provided insights into the basin's stratigraphy, with an update to the Permo-Carboniferous succession based on seismic interpretation, borehole data integration, field validation, and paleontological information. However, biostratigraphic subdivision of the Carboniferous section remains challenging due to poorly constrained species definitions, leading to discrepancies in the application of biozonations.

The upper Permian to Lower Triassic sedimentary succession in the southern Bonaparte Basin represents an extensive marginal marine depositional system that hosts several gas accumulations, including the Blacktip gas field that has been in production since 2009. Development of additional identified gas resources has been hampered by reservoir heterogeneity, as highlighted by preliminary results from a post drill analyses of wells in the study area that identify reservoir effectiveness as a key exploration risk. The sedimentary succession that extends across the Permian–Triassic stratigraphic boundary was deposited during a prolonged marine transgression and shows a transition in lithofacies from the carbonate dominated Dombey Formation to the siliciclastic dominated Tern and Penguin formations. Recent improvements in chronostratigraphic calibration of Australian biostratigraphic schemes, spanning the late Permian and Early Triassic, inform our review of available palynological data and re-interpretation and infill sampling of well data. The results provide a better resolved, consistent and up-to-date stratigraphic scheme, allowing an improved understanding of the timing, duration, and distribution of depositional environments of the upper Permian to Lower Triassic sediments across the Petrel Sub-basin and Londonderry High. <b>Citation:</b> Owens R., Kelman A., Khider K., Iwanec J., Bernecker T. (2022) Addressing exploration uncertainties in the southern Bonaparte Basin: enhanced stratigraphic control and post drill analysis for upper Permian plays. <i>The APPEA Journal</i> 62, S474-S479