Australia and Nuna P. G. BETTS 1 *, R. J. ARMIT 1 , J. STEWART 1,5 , A. R. A. AITKEN 2 , L. AILLERES 1 , P. DONCHAK 3 , L. HUTTON 3 , I. WITHNALL 3 & D. GILES 4 1 School of Earth, Atmosphere and Environment, Monash University, Clayton Campus, VIC 3800, Australia 2 Centre for Exploration Targeting, The University of Western Australia (M006), Crawley, WA 6009, Australia 3 Geological Survey of Queensland, Level 10, 119 Charlotte Street, Brisbane, QLD 4000, Australia 4 Centre for Mineral Exploration Under Cover, School of Earth and Environmental Sciences, University of Adelaide, SA, Australia 5 Present address: PGN Geoscience, GPO BOX 1033, Melbourne, VIC 3001, Australia *Corresponding author (e-mail: Peter.Betts@monash.edu) Abstract: The Australian continent records c. 1860 – 1800 Ma orogenesis associated with rapid accretion of several ribbon micro-continents along the southern and eastern margins of the proto-North Australian Craton during Nuna assembly. The boundaries of these accreted micro- continents are imaged in crustal-scale seismic reflection data, and regional gravity and aero- magnetic datasets. Continental growth (c. 1860–1850 Ma) along the southern margin of the proto-North Australian Craton is recorded by the accretion of a micro-continent that included the Aileron Terrane (northern Arunta Inlier) and the Gawler Craton. Eastward growth of the North Australian Craton occurred during the accretion of the Numil Terrane and the Abingdon Seismic Province, which forms part of a broader zone of collision between the northwestern margins of Laurentia and the proto-North Australian Craton. The Tickalara Arc initially accreted with the Kimberley Craton at c. 1850 Ma and together these collided with the proto-North Austra- lian Craton at c. 1820 Ma. Collision between the West Australian Craton and the proto-North Australian Craton at c. 1790– 1760 Ma terminated the rapid growth of the Australian continent. Nuna The geological record shows episodes of rapid con- tinental assembly to form supercontinents. There is a degree of confidence in the configuration of supercontinents formed in the last billion years of Earth’s history (Evans 2013); however, determining the supercontinent configurations beyond a billion years is subjective (Cawood & Hawkesworth 2014) because the rock record becomes more difficult to decipher and high-quality palaeomagnetic data is limited (Pisarevsky et al. 2014). Evidence for a Palaeoproterozoic supercontinent Nuna/Columbia (herein referred to as Nuna) (Rogers & Santosh 2002; Zhao et al. 2002, 2004; Pisarevsky et al. 2014) is supported by palaeomagnetic constraints (Evans & Mitchell 2011; Zhang et al. 2012a; Pisarevsky et al. 2014), tectonic criteria (Karlstrom et al. 2001; Betts et al. 2008, 2011; Doe et al. 2012) and geochemical and geochronology data (Condie & Aster 2010; Condie et al. 2011). However, Nuna’s exact configuration remains uncertain. In most Nuna configurations Australia occupies an important component of the supercontinent (Zhao et al. 2002; Zhang et al. 2012a), with most reconstructions placing eastern Australia and west- ern Laurentia next to each other (Fig. 1a – c). Uncer- tainty remains about the timing of Australia and Laurentia amalgamation during Nuna formation. For example several Nuna reconstructions have Australia and Laurentia together by c. 1740 Ma (Betts et al. 2008; Zhang et al. 2012a), whereas others have proposed that Australia existed as an isolated continent that did not amalgamate to Laur- entia until c. 1600 – 1500 Ma (Eglington et al. 2013; Pisarevsky et al. 2014). The Palaeoproterozoic assembly of Australia is the most significant period of crustal amalgama- tion, with approximately two-thirds of the conti- nent forming between c. 1860 and 1800 Ma (Betts et al. 2002). The internal structure of the Australian continent comprises a collage of cratons, micro- continents and arc terranes that had amalgamated by c. 1700 Ma (Li 2000; Betts & Giles 2006; Cawood From:Li, Z. X., Evans, D. A. D. & Murphy, J. B. (eds) Supercontinent Cycles Through Earth History. Geological Society, London, Special Publications, 424, http://doi.org/10.1144/SP424.2 # 2015 The Geological Society of London. For permissions: http://www.geolsoc.org.uk/permissions. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics. at Monash University on June 4, 2015 http://sp.lyellcollection.org/ Downloaded from