Nubrigyn algal reefs (Devonian), eastern Australia: Allochthonous blocks and megabreccias

Research Article| April 01, 1976 Nubrigyn algal reefs (Devonian), eastern Australia: Allochthonous blocks and megabreccias P. J. CONAGHAN; P. J. CONAGHAN 1School of Earth Sciences, Macquarie University, North Ryde, New South Wales, 2113, Australia Search for other works by this author on: GSW Google Scholar E. W. MOUNTJOY; E. W. MOUNTJOY 2Department of Geological Sciences, McGill University, Montreal, Quebec H3C 3G1, Canada Search for other works by this author on: GSW Google Scholar D. R. EDGECOMBE; D. R. EDGECOMBE 1School of Earth Sciences, Macquarie University, North Ryde, New South Wales, 2113, Australia Search for other works by this author on: GSW Google Scholar J. A. TALENT; J. A. TALENT 1School of Earth Sciences, Macquarie University, North Ryde, New South Wales, 2113, Australia Search for other works by this author on: GSW Google Scholar D. E. OWEN D. E. OWEN 3Department of Geology, Bowling Green State University, Bowling Green, Ohio 43403 Search for other works by this author on: GSW Google Scholar Author and Article Information P. J. CONAGHAN 1School of Earth Sciences, Macquarie University, North Ryde, New South Wales, 2113, Australia E. W. MOUNTJOY 2Department of Geological Sciences, McGill University, Montreal, Quebec H3C 3G1, Canada D. R. EDGECOMBE 1School of Earth Sciences, Macquarie University, North Ryde, New South Wales, 2113, Australia J. A. TALENT 1School of Earth Sciences, Macquarie University, North Ryde, New South Wales, 2113, Australia D. E. OWEN 3Department of Geology, Bowling Green State University, Bowling Green, Ohio 43403 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1976) 87 (4): 515–530. https://doi.org/10.1130/0016-7606(1976)87<515:NARDEA>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation P. J. CONAGHAN, E. W. MOUNTJOY, D. R. EDGECOMBE, J. A. TALENT, D. E. OWEN; Nubrigyn algal reefs (Devonian), eastern Australia: Allochthonous blocks and megabreccias. GSA Bulletin 1976;; 87 (4): 515–530. doi: https://doi.org/10.1130/0016-7606(1976)87<515:NARDEA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The widely known Lower Devonian "algal reef " limestones of the Nubrigyn Formation, New South Wales, are enormous allochthonous blocks contained within a 400-m interval of interbedded mudstones, allodapic carbonates, and megabreccias that form part of a 5,000-m succession of Lower Devonian volcanics and flysch. Previous workers have interpreted these massive limestone bodies to be algal bioherms that developed in sublittoral to littoral environments around volcanic pedestals on a "Nubrigyn shelf." The allochthonous nature of the limestone bodies is clearly indicated by (1) occurrence of a wide range of clast sizes, as much as 1 km across; (2) presence of a wide range of clast types and sizes in close juxtaposition; (3) discordance between stratigraphic facing of the large limestone bodies and stratification in surrounding beds; (4) lack of distinctive and regular facies changes within the limestone bodies, particularly near their margins; (5) abrupt and random truncation of internal fabrics at block margins; (6) lack of an autochthonous volcanic foundation for the "reefs"; and (7) anomalous lithofacies association of the massive bodies of shoal-water limestone with enclosing flysch.The limestones initially formed in a shoal-water carbonate complex to the west upon a geologically persistent volcanic archipelago, the Molong Arch, where source rocks for the Nubrigyn megaclasts and megabreccias crop out in the Lower Devonian Garra Formation and Cuga Burga Volcanics. The Nubrigyn megaclasts were transported eastward as debris flows into the adjacent and relatively deep water Hill End Trough after dislodgement from the eastern margin of the Garra shelf. Megaclasts isolated within hemipelagic mudstones and flysch were presumably transported by sliding or rolling. The loci of accumulation of the debris flows and exotic blocks occupy a meridional basin-margin position between the Molong Arch to the west and the predominantly turbidite-filled Hill End Trough to the east.Other debris-flow megabreccias, many previously unrecognized as having been transported and deposited in this manner, occur in the Paleozoic rocks of the Tasman mobile belt of eastern Australia. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.