Preservation of thermal signature of elevated syn-rift heat flow during multiphase extension: a case study from the Duntroon Sub-basin, Great Australian Bight
Simon Holford A * , Ian Duddy B , Paul Green B , Nick Schofield C , Richard Hillis A and Martyn Stoker AA School of Physics, Chemistry and Earth Sciences, University of Adelaide, SA, Australia.
B Geotrack International, Vic., Australia.
C School of Geosciences, University of Aberdeen, Scotland, UK.
The APPEA Journal 63 S247-S250 https://doi.org/10.1071/AJ22060
Accepted: 16 March 2023 Published: 11 May 2023
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of APPEA.
Abstract
Quantifying the thermal histories of rift basins is important for evaluating their resource and CO2 storage potential because temperature controls hydrocarbon generation, and the diagenesis of reservoir rocks. However, in many rift basins, it is difficult to obtain evidence for elevated heat flow accompanying rifting, since paleotemperature data from drilled sections typically record heating related to post-rift burial. Here we integrate geochemical, geophysical and petrophysical data from the Duntroon Sub-basin, Great Australian Bight, that show how strain-migration during multiphase extension can preserve the signature of syn-rift elevated geothermal gradients. During the late Jurassic–early Cretaceous, rifting was focussed along ~ESE-striking normal fault systems in the northern part of the Duntroon Sub-basin. During the late Cretaceous, strain migrated to the southwest through the development of normal faults which accommodated the deposition of Upper Cretaceous strata. The Echidna-1 well was drilled into a basement high, in the footwall of a late Cretaceous fault system, penetrating ~2.5 km of Lower Cretaceous strata. Paleotemperature proxies define an early Cretaceous paleogeothermal gradient of ~60°C km−1, substantially higher than the present-day gradient. Our results indicate that preserved Lower Cretaceous strata were more deeply buried by ~1 km of additional section, which was likely eroded during an episode of mid-Cretaceous exhumation associated with the migrating locus of rifting; this enabled the preservation of thermal signature of elevated syn-rift heat flow. Similar evidence is also observed in the Otway Basin, demonstrating the regional extent of elevated syn-rift heat flow along the southern Australian margin.
Keywords: exhumation, extension, Great Australian Bight, heat flow, normal faulting, reservoirs, rifting, thermochronology.
Professor Simon Holford is South Australian State Chair of Petroleum Geoscience in the Discipline of Earth Sciences, University of Adelaide. Simon has published ~130 papers on the prospectivity and tectonics of rifted margins, petroleum geomechanics and magmatism in basins. Simon has a PhD from the University of Birmingham and a BSc (Hons) from Keele University. Simon has won multiple awards, including Best Paper prizes at APPEA 2012 and AEGC 2019, Best Extended Abstract at APPEA 2021 and the Geological Society of Australia’s Walter Howchin and ES Hills medals. |
Ian Duddy is a founding Director of Geotrack International Pty Ltd, specialist consultants in thermal history reconstruction for basin modelling. He obtained BSc (Hons) and PhD degrees in Geology from the University of Melbourne and has been involved in researching the thermal evolution of sedimentary basins since 1975. He is a member of PESA and the Geological Society of Australia, which awarded him the Selwyn Medal for significant contributions to Victorian Geology in 2014. |
Paul Green is recently retired from his position as Technical Director of Geotrack International, a private company specialising in thermal history reconstruction in sedimentary basins, and its application to hydrocarbon exploration. He has a PhD from the University of Birmingham, and is the author of over 100 published papers in peer-reviewed journals on fission track analysis and related topics. |
Professor Nick Schofield is Chair in Igneous and Petroleum Geology at the University of Aberdeen. He gained his undergraduate degree in Geology from the University of Edinburgh, before undertaking a PhD at the University of Birmingham investigating the emplacement of sill intrusions. He has worked and published extensively on intrusive and extrusive volcanism within sedimentary basins globally and works closely with the petroleum industry on igneous-related aspects of the subsurface. |
Richard Hillis is Non-Executive Chair of Investigator Resources and Emeritus Professor at the University of Adelaide. He graduated with a BSc (Hons) from Imperial College, and a PhD from the University of Edinburgh. From 2010 to 2018 he was CEO of the Deep Exploration Technologies Cooperative Research Centre (DET CRC) and from 2019 to 2021 Pro Vice-Chancellor (Research Performance) at the University of Adelaide. Richard is a Fellow of ATSE and was South Australian Scientist of the Year 2018. |
Martyn Stoker is a Visiting Research Fellow at the School of Physics, Chemistry and Earth Sciences at the University of Adelaide. He graduated with a BSc (Hons) in Geology from the University of Leicester in 1977 and then a PhD from the University of Liverpool in 1980. Between 1981 and 2016 he worked in the Marine Science Programme of the British Geological Survey in Edinburgh, Scotland, and continues to publish on the tectonostratigraphic development of passive continental margins. |
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