Quarterly Notes Geological Survey of New South Wales September 2011 No 137 A review of Cambrian and Ordovician stratigraphy in New South Wales Abstract We present a comprehensive review of a significant interval spanning 100 million years in the geological history of New South Wales, listing all currently accepted groups, formations and constituent members of Cambrian and Ordovician age. These units are briefly described and placed in their tectonic context, with the most up-to-date biostratigraphic and isotopic age dating assembled to constrain correlations (depicted in 25 representative stratigraphic columns) across orogenic belts and terranes. Rock units previously assigned a Cambrian or Ordovician age, whose names are now obsolete, redundant or are known to be younger, are also discussed or listed in an appendix. The increasingly diverse literature on the Cambrian and Ordovician stratigraphy of the state is reflected in an extensive bibliography. This review is intended to benefit the mineral exploration industry, research workers both locally and overseas, and geological mapping generally by providing a ready reference to Cambrian and Ordovician rocks in NSW. It also indicates where current data are insufficient to resolve precise age determinations and correlations, thereby highlighting those areas that require further work before a complete synthesis of the early Palaeozoic geological history of NSW can be undertaken. Keywords: Cambrian, Ordovician, New South Wales, stratigraphy, biostratigraphy, Delamerian Orogen, Lachlan Orogen, New England Orogen, Narooma Terrane. Introduction The Cambrian and Ordovician periods span an throughout the Ordovician (Glen 2005; Glen et al. 2009). interval of almost exactly 100 million years, from Cambrian rocks are therefore, in comparison with 542–443 Ma, during which the New South Wales Ordovician strata, relatively poorly represented areally portion of the Tasmanides expanded from restricted in NSW. They are best known from the Koonenberry accumulation on the Delamerian continental margin Belt in the far west of the state (Figure 1), the subject of a and a few distant seamounts during the Cambrian, to regional mapping program completed by the Geological an extensive complex of depositional settings including Survey of New South Wales (Greenfield et al. 2010). back-arc basin, volcanic island arc and offshore terranes As a result of numerous palaeontological studies in AUTHORS I.G. Percival1, C.D. Quinn2 and R.A. Glen2 1 Geological Survey of New South Wales, W.B. Clarke Geoscience Centre, Londonderry, NSW 2753 2 Geological Survey of New South Wales, 516 High Street, Maitland, NSW 2320 © State of New South Wales through the Division of Resources and Energy, 2011 Papers in Quarterly Notes are subject to external review. External reviewer for this issue was Dr Barry Webby, Honorary Associate, Earth and Planetary Sciences, Macquarie University. His assistance is appreciated. Quarterly Notes is published to give wide circulation to results of studies in the Geological Survey of New South Wales. Papers are also welcome that arise from team studies with external researchers. Contact: [email protected] ISSN 0155-3410 Geological Survey of New South Wales Contents the past two decades, the stratigraphy of this region is much better known than was the case for the synthesis Abstract 1 of Shergold et al. (1985), which was largely reliant on Introduction 1 unpublished thesis mapping by Warris (1967). The present review summarises the most recently available Delamerian Orogen 5 biostratigraphic data for the Koonenberry Belt to enable Koonenberry Belt 5 better-constrained correlation with other regions in Thomson Orogen 13 the Delamerian Orogen, such as those in the Flinders Ranges of South Australia. Elsewhere in NSW, very Lachlan Orogen — continental margin terranes 13 localised occurrences of fossiliferous ‘Middle’ Cambrian Albury–Bega Terrane 14 rocks (represented by limestone clasts) have been Hermidale Terrane 19 documented from Batemans Bay on the south coast, and in blocks along the Peel–Manning Fault system in the Oceanic crust and associated units 20 New England Orogen southeast of Tamworth. Cherts at Macquarie Arc 21 the base of the succession at Narooma on the south coast are of Late Cambrian age, and the Adaminaby Group in Narooma Terrane 26 this area also spans the Cambro-Ordovician boundary New England Orogen 27 (Glen et al. 2004). Though direct age control is lacking, Tamworth Belt 27 serpentinite in the Port Macquarie Block is inferred to Port Macquarie Block 28 be Cambrian. Ordovician rocks occupy approximately 20% Synthesis 28 of surface exposures in NSW (Figure 2), with a Acknowledgements 29 considerably greater subsurface extent. They host some References 29 of the most productive metalliferous deposits in the state. Largely due to their economic importance these Appendix 39 rocks have been the focus of recent and continuing mapping programs and associated research studies by the Geological Survey of New South Wales and other institutions. A large number of publications describing Cover photograph: View towards Dunhill Bluff from Fossil Hill, showing the thin-bedded Fossil Hill Limestone Ordovician rocks in NSW, many in specialist journals, and the lower part of the overlying massive Belubula have appeared since the Australasia-wide synthesis Limestone. Both units are of Late Ordovician age. of Webby et al. (1981). It is therefore timely to review (Photographer: S Meakin). the stratigraphic nomenclature established over the past three decades in order to provide a convenient synthesis from which to develop local and state-wide correlations. For that part of the Macquarie Arc in central NSW, the recent stratigraphic review of Percival Production co-ordination: Geneve Cox and Glen (2007) stands with some minor revisions. That review was largely built on the results of regional Geological editor: Simone Meakin mapping programs for the Bathurst, Dubbo and Forbes 1:250 000 sheet areas, combined with substantial Geospatial information: Cheryl Hormann research input from CODES (Centre of Excellence in Layout and charts: Carey Martin Ore Deposits, at the University of Tasmania). Extensive deep marine basins dominated by clastic sedimentary rocks of turbiditic origin, associated pelagic deposits and graptolitic shales, form the Albury–Bega Terrane and Hermidale Terrane in the centre and south of NSW (modified by Glen et al. 2009 after Glen 2005). Together with the chert-dominated oceanic terrane localised around Narooma on the far south coast (Glen et al. 2004), these deep marine sequences have only relatively recently become stratigraphically subdivisible The information contained in this publication is based on knowledge and understanding using conodont-based biostratigraphic zones. This at the time of writing (June 2011, revised October 2011). However, because of advances allows more precise correlations with the well-known in knowledge, users are reminded of the need to ensure that information upon which turbidite-dominated and graptolitic shale successions they rely is up to date and to check currency of the information with the appropriate of Victoria, the stratigraphy of which were recently officer of the Division of Resources and Energy, or the user’s independent adviser. synthesised by VandenBerg et al. (2000), Fergusson and 2 September 2011 Figure 1. Schematic map of the New South Wales portion of the southern Tasmanides showing distribution of Cambrian rocks in a) Delamerian Orogen and b) New England Orogen. Numbers refer to stratigraphic sequences discussed in text and depicted in Figure 5. Quarterly Notes 3 Figure 2. Schematic map of the New South Wales portion of the southern Tasmanides showing distribution of Ordovician rocks in a) Delamerian Orogen and b) Lachlan Orogen, New England Orogen and Narooma Terrane. Numbers refer to stratigraphic sequences discussed in text and depicted in Figure 5. 4 September 2011 VandenBerg (2003), and Glen et al. (2009). Ordovician Restricted to a small area of exposure on the far south rocks of the New England Orogen are sparsely coast of the state, the Narooma Terrane (Glen et al. 2004) represented by shallow water lithologies including was accreted to the Albury–Bega Terrane during the limestone (some reworked into younger strata) along Late Ordovician. The stratigraphy of one or more poorly the Peel Fault, together with deep water sediments and known and as-yet unnamed oceanic floor terrane(s) pillow basalts of an accretionary complex in the Port associated with serpentinised belts in southern NSW is Macquarie region. Although areally restricted, they the focus of current work. provide critical tie points in correlations to rocks of the Lachlan Orogen. Delamerian Orogen Chronostratigraphic subdivisions of the Cambrian and Ordovician periods have been the subject of Further details of the stratigraphic units discussed in the ongoing revision in recent years. For the Ordovician we following section are provided in Greenfield et al. (2010). use a timescale based on that of Sadler et al. (2009), and Only the most significant fossil occurrences necessary for the Cambrian that of Shergold and Cooper (2004), to support biostratigraphic correlations are given in this modified internally with international subdivisions review; full listings are presented in Percival (2010). recommended by the respective stratigraphic subcommissions and ratified by the International Koonenberry Belt (Figure 5, columns 1–5) Commission on