New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure … · 2019. 8. 13. · • combined with evidence of evaporitic cycles this suggests an ‘evaporitic

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


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


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


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


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


• 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


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


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

?


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


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??


• 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


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


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.


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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Documents

New insights into the Neoproterozoic to early Palaeozoic stratigraphy, structure … · 2019. 8. 13. · • combined with evidence of evaporitic cycles this suggests an ‘evaporitic