New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Verity Normington1, Chris Edgoose1, Nigel Donnellan1, Anett Weisheit1, and Charles Verdel1 1NTGS New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin NTGS Amadeus Basin projects have enabled us to develop some new insights into: • stratigraphy and stratigraphic relationships • evolution of palaeogeography and basin architecture • the style and effects of two major, intracratonic orogenic events Alice Springs Yulara Palaeozoic solid geology Neoproterozoic New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Brief overview • Extensive (~170,000 km2) Neoproterozoic – Devonian intracratonic sedimentary basin • Basement comprised of Musgrave Province (south) and Aileron and Warumpi provinces (north) • Affected by two major intracratonic orogenic events - Petermann Orogeny (~580-530 Ma) N and NNE directed Georgina Basin - focused in Musgrave Province and SW basin margin Ngalia Basin Alice Springs Orogeny (~ 450- 300 Ma) S directed Aileron Province Irindina - focused in Aileron/Warumpi/Irindina provinces and Warumpi Province Province northern basin margin • significant halotectonic activity related to evaporates in basal part of succession Eromanga Basin Musgrave Province New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Major focus on Neoproterozoic succession Stratigraphy • 2014 -NE basin field-based study – characterise Neoproterozoic succession where best exposed • 2015 – 2017 - 100K and 250K scale mapping in the central part of the basin (HENBURY) where the Neoproterozoic succession had been grouped into two informal units – Inindia beds and Winnall beds 2014 2015 – Alice Springs 2017 Yulara Palaeozoic solid geology Neoproterozoic New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Stratigraphy 2013 Neoproterozoic – early Palaeozoic Current Neoproterozoic – early Palaeozoic stratigraphy (Edgoose 2013) stratigraphy (Normington 2018) NE • Bitter Springs Group • Wallara Fm in outcrop and full definition • Updated type sections and descriptions for rest of Neoproterozoic succession New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Inindia beds Stratigraphy sandstone, siltstone, chert, brecciated chert, conglomerate, diamictite, dolostone, limestone, jasper, stromatolitic dolostone, shale Inindia beds New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Winnall beds Stratigraphy Winnall Northeast beds • Defined and described mappable formations • Stratigraphic relationships are complex as the formations present vary from east to west New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Stratigraphy Petermann Sandstone Max dep age - ca 510 Ma Detrital zircon geochronology can assist with resolving stratigraphic relationships Quandong Conglomerate was interpreted to be early Cambrian on the 1st edition map of Deception Sandstone HENBURY, and considered to be a local molasse Max dep age - ca 515 Ma unit probably deposited in response to uplift associated with the ~580-530 Ma Petermann Cambrian Orogeny. Tempe Formation Max dep age - ca 520 Ma Quandong Conglomerate Max dep age – ca 630 Ma Neoproterozoic HENBURY 250K 1st edition New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Chookla member Stratigraphy Max dep age - ca 620 Ma Gloaming Formation Group Max dep age – ca 640 Ma eoproterozoic N Winnall Late Quandong Conglomerate Max dep age – ca 630 Ma • Field relationships - Quandong Cg overlies Areyonga Fm and underlies probable Gloaming Fm (Winnall Grp) • It has similar maximum deposition age to overlying Winnall Grp. • Has similar dominant 1200-1050 Ma provenance • In contrast only minor older detrital component, similar to the underlying Areyonga Fm – therefore locally sourced • Pre-dates Petermann Orogeny – local uplift event New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Stratigraphy • Comparative probability density plot of all units in HENBURY • Comprises entire basin succession above Bitter Springs Group • Includes several Cambrian siliclastic units unique to this area • Palaeozoic units have substantial 500-700 Ma population • Quandong conglomerate confirmed as typical Neoproterozoic spectra Palaeozoic • Units dominated by siltstones have significantly less older and younger inheritance – related to depositional environment rather than change in source region/s Neoproterozoic New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin • Revisiting stratigraphic logs of key NT drillholes and outcrop mapping by GSWA has shown the Palaeogeography Neoproterozoic succession thickens to west and NW Neoproterozoic • Neoproterozoic depocentre in NE • This apparent palaeogeography has been overprinted by two major orogenic events – however likely to still represent remains of original depocentres • 3D modelling (COBRA) supports earlier interpretation that an interval of non-magnetic rocks sits between the estimated thickness of the known Amadeus Basin succession and magnetic basement – thicker than estimated Neoproterozoic? Aralka Formation Updated distribution • Basin-wide • Thins in basin centre then thickens significantly to the Haines west and Allen 2014. ? Wallara Formation Updated distribution • basin-wide Haines • overall westward thickening and Allen 2014. New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Post Petermann Orogeny Palaeogeography • restricted foreland basin adjacent to orogenic front Palaeozoic • central and southern basin areas dominated by southern platform with thin (central) or absent (southern) Palaeozoic succession • depocentres developed in northern basin, north of a ??central ridge?? • Lithofacies variations in some units between southern platform succession and depocentre succession supports the current basin architecture model Northern depocentres ??central • depositional environment of Stairway ss is southern ridge?? shallow marine on both depocentre platform (thicker) and on platform (thinner) foreland basin • in both areas lithofacies subunits can be identified - not a condensed section • lithofacies are different in each element New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Arumbera Sandstone Maidment 2005 Palaeogeography Detrital zircon geochronology provides further insight to palaeogeography and basin architecture over time Neoproterozoic • NE mostly dominated by Aileron Province • Central basin mostly dominated by Musgrave Province Palaeozoic Palaeozoic • No change in provenance pattern in central basin • Major influx of new, younger source region/s • Significant shift to Musgrave dominance in NE Neoproterozoic 580-530 Ma Petermann Orogeny Aileron Province Neoproterozoic Musgrave Province New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin • Major new younger unknown source areas post Petermann Orogeny – east or west? Palaeogeography • Significant redevelopment of basin architecture/palaeogeography Palaeozoic • Need to consider in broader context than just Amadeus Basin • Petermann Orogeny interpreted to cause break up of Neoproterozoic Centralian superbasin A • Beginning development of Palaeozoic eastern Australia • Major Palaeozoic basins in western Australia • Plate tectonic setting Palaeozoic Northern depocentres ??central southern ridge?? platform foreland basin Neoproterozoic New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin Wong 2018 Heavitree Formation; zircon (Al-Kiyumi 2018, NTGS) Palaeogeography 1 2 3 • U-Pb ages and εHf show that the Heavitree Formation in the northern basin is dominantly sourcing the Arunta Region, Musgrave Province and the eastern fold belts of the Mt Isa Province. Selected Neoproterozoic-Cambrian units; zircon (Al-Ghafri 2018, SANTOS) • Arumbera, Pertatataka and Areyonga formations in the central basin are dominantly sourced from the Musgrave Province • Pioneer Sandstone and Areyonga Formation in the NE of the basin are dominantly sourced from the Aileron Province Heavitree Fm Selected Neoproterozoic-Palaeozoic units; zircon and Apatite (Wong 2018, Al-Kiyumi 2018 SANTOS) central to southern basin Prominent zircon U-Pb age peak Musgrave Province 2 Secondary zircon U-Pb age peak Arunta Region 3 Early zircon U-Pb age peak (ca. 560 – 646 Ma) Paterson, Rudall Province?? 1 Apatite grains are fully reset and do not provide provenance information New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin C and Sr Isotopes, Neoproterozoic Carbonates (AlKhanjari 2018, Palaeogeography SANTOS) central basin • δ13C trends correlate with both local and global Neoproterozoic C isotope record • 87Sr/86Sr data generally more