Reeve, MT, Magee, C orcid.org/0000-0001-9836-2365, Jackson, CA-L et al. (2 more authors) (2022) Stratigraphic record of continental breakup, offshore NW Australia. Basin Research, 34 (3). pp. 1220-1243. ISSN 0950-091X
Abstract
Continental breakup involves a transition from rapid, fault-controlled syn-rift subsidence to relatively slow, post-breakup subsidence induced by lithospheric cooling. Yet the stratigraphic record of many rifted margins contain syn-breakup unconformities, indicating that episodes of uplift and erosion interrupt this transition. This uplift has been linked to mantle upwelling, depth-dependent extension and/or isostatic rebound. Deciphering the breakup processes recorded by these unconformities and their related rock record is challenging because uplift-associated erosion commonly removes the strata that help constrain the onset and duration of uplift. We examine three major breakup-related unconformities and the intervening rock record in the Lower Cretaceous succession of the Gascoyne and Cuvier margins, offshore NW Australia, using seismic reflection and borehole data. These data show the breakup unconformities are disconformable (non-erosive) in places and angular (erosive) in others. Our recalibration of palynomorph ages from rocks underlying and overlying the unconformities shows: (i) the lowermost unconformity developed between 134.98–133.74 Ma (Intra-Valanginian), probably during the localisation of magma intrusion within continental crust and consequent formation of continent–ocean transition zones (COTZ); (ii) the middle unconformity formed between ca. 134 and 133 Ma (Top Valanginian), possibly coincident with breakup of continental crust and generation of new magmatic (but not oceanic) crust within the COTZs; and (iii) the uppermost unconformity likely developed between ca. 132.5 and 131 Ma (i.e. Intra-Hauterivian), coincident with full continental lithospheric breakup and the onset of seafloor spreading. During unconformity development, uplift was focussed along the continental rift flanks, likely reflecting flexural bending of the crust and landward flow of lower crust and/or lithospheric mantle from beneath areas of localised extension towards the continent (i.e. depth-dependent extension). Our work supports the growing consensus that the ‘breakup unconformity’ is not always a single stratigraphic surface marking the onset of seafloor spreading; multiple unconformities may form and reflect a complex history of uplift and subsidence during continent–ocean transition.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2022 The Authors. Basin Research published by International Association of Sedimentologists and European Association of Geoscientists and Engineers and John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
Keywords: | basin; breakup; palynology; rift; seismic reflection; unconformity; uplift |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 11 Jan 2022 11:14 |
Last Modified: | 25 Jun 2023 22:52 |
Status: | Published |
Publisher: | Wiley |
Identification Number: | 10.1111/bre.12656 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:182222 |