The Exploring for the Future (EFTF) program is an initiative by the Australian Government dedicated to boosting investment in resource exploration in Australia. Geoscience Australia’s EFTF Energy program is aimed at improving the understanding of the petroleum resource potential of Australia. A key to understanding resource potential and basin evolution is a reliable time frame to correlate rock units. This palynological reconnaissance study focusses on the acid-resistant organic-walled microfossils (or palynomorphs) recovered from 42 samples taken within the fully cored Lower Ordovician Nambeet Formation (1354.80–2435.04 mRT) in the Barnicarndy 1 stratigraphic well, located in the Barnicarndy Graben, Canning Basin. The lack of palynomorph recovery from the Barnicarndy Formation, Yapukarninjarra Formation, and Neoproterozoic Yeneena Basin, also intersected in this well, means that the age of those units remain undated using micropalaeontological methods. The purpose of this study is to assess the yield and preservation of recovered palynomorphs, and determine their utility for regional, and international, correlation of the Lower Ordovician sedimentary section. Although the total organic matter content of the sampled Lower Ordovician core is typically low (average ≤0.2 wt%), reflecting sediment deposition in an oxidising, open marine environment, a diverse suite of palynomorphs has been identified and includes: acritarchs (of probable algal origin); other algal microfossils (including green algae, or prasinophytes); probable cyanobacteria; cryptospores (derived from the earliest land plants); graptolites and chitinozoans (both from extinct marine groups); scolecodonts (detached elements of worm jaws); and organic-walled tubes, some of which are of either probable fungal or cyanobacterial origin. Digital images accompany this record and include examples of all of these aforementioned microfossils. Microfossil yield per sample is, mostly, low; and preservation ranges from poor, where specimens are either fragmentary and/or distorted by pyrite crystal growth, to good; and commonly both preservation states occur together within the same sample. As with the admixture of preservation states per sample, palynomorph colour, typically used as an indicator of thermal maturity of organic matter, commonly ranges from thermally mature (brown) to over mature (black), often within the same Lower Ordovician core sample. This is tempered by the fact that these observations are based, mostly, on oxidised kerogen preparations, but, the relative maturity indicators remain valid. The occurrence of acritarchs assigned to the Rhopaliophora pilata–R. palmata complex, together with Athabascaella playfordii, and Aryballomorpha grootaertii, allows correlation with assemblages previously recovered from the Nambeet Formation intersected in two petroleum exploration wells in the Canning Basin (Samphire Marsh 1, type section; and Acacia 2). These species also occur globally, with A. grootaertii recovered from sedimentary rocks in southern China and Canada that have been independently dated as Early Ordovician, late Tremadocian–early Floian (about 475–482 Ma). Conodont faunas from cores in Barnicarndy 1 record the same (late Tremadocian–early Floian) age, which enhances the utility of A. grootaertii for age dating. The dates also demonstrate that the Barnicarndy 1 well intersects some of the oldest Paleozoic sedimentary rocks in the Canning Basin. There are compositional differences between the palynological assemblages from the younger Samphire Marsh Member and underlying Fly Flat Member of the Nambeet Formation which, despite difficulties in sample processing, are genuine and reflect changes in the depositional environment. Most obvious is the record of Gloeocapsomorpha prisca and ?Eomerismopedia maureeniae, both of probable cyanobacterial affinity, with in situ occurrences in the Lower Ordovician Samphire Marsh Member. Earlier studies suggested that G. prisca was confined to younger (Middle) Ordovician palynological assemblages in the Canning Basin, and its common abundance was used as a biozone marker, but the occurrences reported here and in unpublished studies, have shown that this is no longer applicable. In younger Ordovician formations in the Canning Basin (notably the upper Goldwyer Formation), and globally, G. prisca is an important organism contributing to the hydrocarbon potential of Paleozoic marine source rocks. If present in greater abundance elsewhere in the basin, it could increase the petroleum prospectivity of the Nambeet Formation. A distinctively shaped acritarch, of probable algal origin, assigned to the genus Dactylofusa is restricted to an assemblage from the Fly Flat Member, and may be useful for future basinal biozone correlation. Most samples from the Samphire Marsh Member contain early land-plant spores, of probable bryophyte affinity, that sometimes occur together with irregularly-shaped spore clusters, likely derived from aeroterrestrial charophyte algae; both of which are collectively known as cryptospores. In addition, Grododowon orthagonalis, superficially similar to E. maureeniae and recorded in some samples from the Samphire Marsh Member, is also considered to be of charophyte algal origin. The cryptospores include the species Dyadospora murusattenuata, Tetraplanarisporites sp., and Laevolancis divellomedium. Collectively, these cryptospores are important as they herald the first emergence of plants onto wetlands during the Early Ordovician; and being of late Tremadocian–early Floian age, they are amongst the oldest land-plant spores known in Australia and globally. The record of cryptospores from Barnicarndy 1 enhances those recently reported from the Nambeet Formation in Samphire Marsh 1, and from the lower Goldwyer Formation in Theia 1. Locally, the cryptospore record demonstrates a supply of terrestrial material into the marine environment during deposition of the Samphire Marsh Member. Globally, records of these cryptospores contribute to the understanding of the evolution and geographic distribution of the earliest land flora. Inevitably, there are microfossils found in this study that could be described as new species, and a detailed systematic study of all fossil groups is recommended to realise their utility for zonal correlation and age dating. The palynological data presented here provide complementary information to the conodont age dating, organic petrological, and organic geochemical studies conducted on the Barnicarndy 1 core. Collectively, these studies contribute to a better understanding of the depositional history and hydrocarbon prospectivity of the Canning Basin.

This report presents palynological data compiled and analysed as part of the National Groundwater Systems (NGS) Project. NGS is part of Exploring for the Future (EFTF)—an eight year, $225 million Australian Government funded geoscience data and information acquisition program focused on better understanding the potential mineral, energy and groundwater resources across Australia. This study builds on previous work (Hannaford et al., 2022) undertaken as part of the ‘Assessing the Status of Groundwater in the Great Artesian Basin’ project, commissioned by the Australian Government through the National Water Infrastructure Fund – Expansion. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, examined an additional 688 boreholes across the GAB and compiled 149 new palynological summary sheets having Jurassic‒Cretaceous succession, with reviewed palynology data (down to total depth). The combined borehole palynological data examined from this study and the previous GAB work (Hannaford et al., 2022) is compiled in Appendix B4. The combined dataset totals 1,394 boreholes examined and 652 with palynology in the stratigraphic interval of interest, 102 of these boreholes contained Cenozoic palynology relevant to the Lake Eyre Basin. This information has been used to revise stratigraphic correlations across the GAB (Norton & Rollet, 2022 and 2023). Initial review of the stratigraphy in the Lake Eyre Basin (LEB) compiled existing palynology from outcrop, mineral and petroleum boreholes. An additional 28 boreholes in the Upper Darling Floodplain region were examined, 16 of which contained relevant palynology. The main palynological data infill in the GAB and LEB region during this follow-up study focused on: 1. Collecting, processing and analysing new biostratigraphic data on 149 key boreholes particularly across the Eromanga and Surat basins boundary. The study focussed on integrating data in New South Wales from the southern Surat Basin and central Eromanga Basin. 2. Further palynological data infill and palynological analysis on 15 samples from 7 boreholes in the western Eromanga Basin to assess difficulties in correlating the stratigraphy across the Algebuckina Sandstone. 3. Compiling existing analyses and update any historical palynological data in the Lake Eyre Basin to reflect the latest zonation scheme developed in this study. The new palynological data combined with new zircon data from other studies in the Carpentaria and Surat basins (Foley et al., 2020, 2021, 2022; La Croix et al., 2022, respectively) provides information on the tie to the geological timescale and help refine the chronostratigraphic chart that summarises stratigraphic correlations across the Carpentaria, Surat and Eromanga basins of Hannaford et al. (2022). All boreholes were examined outside of the Cooper and Bowen basins boundaries with selected boreholes around transects defined for stratigraphic correlation review through the Cooper and Bowen basin outlines (Norton & Rollet, 2022 and 2023). As a result, most of the remaining unreviewed palynological data lies within the Cooper and Bowen basins. The results of the palynology data infill in the western Eromanga Basin, in South Australia and Northern Territory, show that the Algebuckina Sandstone section is dominated by clean sandstone and so the cuttings samples were also dominated by sand. Although attempts were made to concentrate the shale from the cuttings in the thicker shale mid formation, this did not yield results, due to the amount of caved Cretaceous material. An initial assessment of the Lake Eyre Basin palynological data and zonation scheme was undertaken using information derived from water, mineral and petroleum boreholes. This provides an initial state of knowledge for the Lake Eyre Basin that can be built on in the future. Recommendations are provided for further studies to build a better understanding of the stratigraphy in the Great Artesian and Lake Eyre basins.