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
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
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Palaeozoic
Neoproterozoic
Alice Springs
Yulara
solid geology
• Extensive (~170,000 km2) Neoproterozoic – Devonian intracratonicsedimentary 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- focused in Musgrave Province and SW basin margin
Alice Springs Orogeny (~ 450- 300 Ma) S directed- focused in Aileron/Warumpi/Irindina provinces and northern basin margin
• significant halotectonic activity related to evaporates inbasal part of succession
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Brief overview
Ngalia Basin
Aileron Province
Georgina Basin
Musgrave Province
EromangaBasin
Irindina ProvinceWarumpi Province
Palaeozoic
Neoproterozoic
Yulara
Alice Springs
solid geology
Major focus on Neoproterozoic succession
• 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 – Inindiabeds and Winnall beds
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Stratigraphy
2014
2015 –2017
StratigraphyNew insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
• Bitter Springs Group• Wallara Fm in outcrop
and full definition• Updated type sections and
descriptions for rest of Neoproterozoic succession
2013 Neoproterozoic – early Palaeozoic stratigraphy (Edgoose 2013)
Current Neoproterozoic – early Palaeozoic stratigraphy (Normington 2018)
NE
sandstone, siltstone, chert, brecciated chert, conglomerate, diamictite, dolostone,limestone, jasper, stromatolitic dolostone, shale
StratigraphyInindia bedsNew insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Inindia beds
Stratigraphy
Northeast
Winnall bedsNew insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Winnallbeds
• Defined and described mappable formations
• Stratigraphic relationships are complex as the formations present vary from east to west
Stratigraphy
Quandong ConglomerateMax dep age – ca 630 Ma
Deception SandstoneMax dep age - ca 515 Ma
Tempe FormationMax dep age - ca 520 Ma
Petermann SandstoneMax dep age - ca 510 Ma
Neo
prot
eroz
oic
Cam
bria
n
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
HENBURY 250K 1st edition
Quandong Conglomerate was interpreted to be early Cambrian on the 1st edition map of HENBURY, and considered to be a local molasseunit probably deposited in response to uplift associated with the ~580-530 Ma PetermannOrogeny.
Detrital zircon geochronology can assistwith resolving stratigraphic relationships
Stratigraphy
Quandong ConglomerateMax dep age – ca 630 Ma
Gloaming Formation Max dep age – ca 640
Ma
Chookla memberMax dep age - ca 620 Ma
Win
nall
Gro
up
Late
Neo
prot
eroz
oic
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
• Field relationships - Quandong Cg overlies Areyonga Fmand 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• Units dominated by siltstones have significantly less older and
younger inheritance – related to depositional environment rather than change in source region/s
Neo
prot
eroz
oic
Pala
eozo
ic
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Palaeogeography• Revisiting stratigraphic logs of key NT drillholes and outcrop mapping by GSWA has shown the Neoproterozoic succession thickens to west and NW
• 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?
Updated distribution • Basin-wide • Thins in basin centre then
thickens significantly to the westHaines
and Allen
2014.
Aralka Formation
Updated distribution • basin-wide • overall westward thickeningHaines
and Allen
2014.
Wallara Formation
Neoproterozoic
?
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
PalaeogeographyPalaeozoic• restricted foreland basin adjacent to orogenic front
• 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
Post Petermann Orogeny
• depositional environment of Stairway ss is shallow marine on both depocentre(thicker) and on platform (thinner)
• in both areas lithofacies subunits can be identified - not a condensed section
• lithofacies are different in each element
Northern depocentres
foreland basin
southern platform
??central ridge??
Palaeogeography
Aileron Province
Musgrave Province
580-530 Ma Petermann Orogeny
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Neo
prot
eroz
oic
Pala
eozo
icMaidment 2005
Detrital zircon geochronology providesfurther insight to palaeogeography and
basin architecture over time
Neoproterozoic• NE mostly dominated by Aileron Province• Central basin mostly dominated by Musgrave
Province
Palaeozoic• No change in provenance pattern in
central basin • Major influx of new, younger source region/s• Significant shift to Musgrave dominance
in NE
Arumbera Sandstone
Neo
prot
eroz
oic
Northern depocentres
foreland basin
southern platform
??central ridge??
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?• Significant redevelopment of basin architecture/palaeogeography• 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
Neo
prot
eroz
oic
Pala
eozo
ic
PalaeogeographyPalaeozoic
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
PalaeogeographyHeavitree Formation; zircon (Al-Kiyumi 2018, NTGS)• 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
Selected Neoproterozoic-Palaeozoic units; zircon and Apatite (Wong 2018, SANTOS) central to southern basin
Prominent zircon U-Pb age peak Musgrave Province Secondary zircon U-Pb age peak Arunta Region Early zircon U-Pb age peak (ca. 560 – 646 Ma) Paterson, Rudall Province??
2
31
Apatite grains are fully reset and do not provide provenance information
Heavitree FmAl-Kiyumi 2018
1 2 3
Wong 2018
C and Sr Isotopes, Neoproterozoic Carbonates (AlKhanjari 2018, SANTOS) central basin• δ13C trends correlate with both local and global Neoproterozoic C
isotope record• 87Sr/86Sr data generally more radiogenic than global
Neoproterozoic Sr isotope record, suggesting progressive basin restriction
Palaeo-depositional environments and redox implications of Cambrian Carbonates (Albusaidi 2018, NTGS) NE basin• Ce anomaly data suggest progressive changes from oxygenated
to more anoxic waters up the stratigraphy.• 87Sr/86Sr record is close to the middle Cambrian global palaeo-
seawater trend • combined with evidence of evaporitic cycles this suggests an
‘evaporitic seaway’ setting in the Amadeus Basin during middle Cambrian
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Palaeogeography
Albusaidi 2018
Schematic ~ N-S sectionHenbury Special 100K
Structure
• 580-530 Ma Petermann Orogeny structures in the southern and central Amadeus Basin are thick-skinned, north- to northeast-directed fault-propagation folds, possibly re-activating pre-existing basement structures.
• 450-300 Ma Alice Springs Orogeny partly reactivated earlier structures and overprinted them by several sets of 100 km long, south-directed fault-bend folds and fault-propagation folds
• Late sets of thick-skinned, oblique-slip to strike-slip faults caused disruption of pre-existing structures.
New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Western half of 1:500K pre-Mesozoic interpreted geologyThe first detailed structural analysis of the central basin through integration of structural observations with interpretation of geophysical data -
Aileron Province
Musgrave Province
Mapping - western basin 2019 New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure and palaeogeography of the Amadeus Basin
Palaeozoic
Neoproterozoic
Yulara
Alice Springs
solid geology
LAKE AMADEUSBLOODSRANGE
HENBURY
• Continue stratigraphic revision and structural analysis westwards - LAKE AMADEUS, northern BLOODS RANGE, outlying areas– Inindia beds and Winnall Group
• Correlations with WA stratigraphy (GSWA) for cross border seamless geology
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