central central Australian Australian

ProjectProject

Lecture 15Lecture 15

Main geological Main geological elementselements

Palaeoproterozoic and Palaeoproterozoic and Mesoproterozoic cratons - granitoids, Mesoproterozoic cratons - granitoids, gneiss, schistgneiss, schist

Neoproterozoic to late Paleozoic Neoproterozoic to late Paleozoic sedimentary basinssedimentary basins

Tertiary weathering and sedimentary Tertiary weathering and sedimentary plains; some extensive dune fieldsplains; some extensive dune fields

Alluvial outwash adjacent to riversAlluvial outwash adjacent to rivers

Arunta Block & Amadeus Arunta Block & Amadeus BasinBasin

Arunta BlockArunta Block

Extensive c. 1870 Ma sediments and volcanicsExtensive c. 1870 Ma sediments and volcanics High-grade metm, defm, granite at c. 1820 MaHigh-grade metm, defm, granite at c. 1820 Ma Uplift, re-exposure before 1820-1780 Ma Uplift, re-exposure before 1820-1780 Ma

Reynolds Range-Hatches Creek GroupsReynolds Range-Hatches Creek Groups High-grade metm and defm at c. 1770 Ma, High-grade metm and defm at c. 1770 Ma,

1580 Ma1580 Ma Southern Arunta - different - 1680 Ma gneiss Southern Arunta - different - 1680 Ma gneiss

defm metm, joined to rest at c. 1600 Madefm metm, joined to rest at c. 1600 Ma

Musgrave BlockMusgrave Block

C.1550 and 1300 Ma protoliths to high-C.1550 and 1300 Ma protoliths to high-grade gneissgrade gneiss

Granulite faces events at c. 1300, 1200 Granulite faces events at c. 1300, 1200 Ma with extensive felsic magmatismMa with extensive felsic magmatism

C. 1080 Ma Giles Complex and C. 1080 Ma Giles Complex and extensive volcanism on western end of extensive volcanism on western end of blockblock

1000 and 800 Ma dykes1000 and 800 Ma dykes C. 550 ma Petermann Orogeny C. 550 ma Petermann Orogeny

Amadeus & Georgina Amadeus & Georgina BasinsBasins Neoproterozoic basins abundant in AustraliaNeoproterozoic basins abundant in Australia

Mostly weakly deformed, except in Adelaide Mostly weakly deformed, except in Adelaide foldbeltfoldbelt

Inconsistent mostly shallow marine Inconsistent mostly shallow marine sedimentation from c. 900 Ma to Devoniansedimentation from c. 900 Ma to Devonian

Sandstone, siltstone, carbonate dominateSandstone, siltstone, carbonate dominate Depo-centres changed with timeDepo-centres changed with time Current basin margins have little to do with Current basin margins have little to do with

deposition, mostly related to deformation at c. deposition, mostly related to deformation at c. 550 Ma (south Amadeus), Ordovician and 550 Ma (south Amadeus), Ordovician and Devonian (north Amadeus, Georgina)Devonian (north Amadeus, Georgina)

Exposed Georgina dominated by Cambrian Exposed Georgina dominated by Cambrian siltssilts

Cretaceous and TertiaryCretaceous and Tertiary

High sea-levels, craton subsidence High sea-levels, craton subsidence lead to much of inland eastern lead to much of inland eastern Australia covered by shallow seas in Australia covered by shallow seas in Mesozoic periods (J, K)Mesozoic periods (J, K)

Sediments later concentrate opal Sediments later concentrate opal and dinosaur fossils, inland gas and dinosaur fossils, inland gas fieldsfields

Tertiary - intense weathering to Tertiary - intense weathering to form duricrusts and ferricrusts, now form duricrusts and ferricrusts, now exposed as breakawaysexposed as breakaways

Western side of GA basin lower than Western side of GA basin lower than east - bubbler springs east - bubbler springs

Specifics - AliceSpecifics - Alice

Scene and geophysical surveys Scene and geophysical surveys straddle the northern margin of the straddle the northern margin of the AmadeusAmadeus

Need structural diagram and then Need structural diagram and then simple 3 fold classification (Arunta, simple 3 fold classification (Arunta, Amadeus, clay)Amadeus, clay)

Basement stratigraphy dominated by Basement stratigraphy dominated by separating granite batholiths, separating granite batholiths, metaseds etc, ?mafic dykesmetaseds etc, ?mafic dykes

PhysiographyPhysiography

Dominated by the east-north-east-trending McDonnell Ranges

High ranges and hills are made up mostly of Proterozoic crystalline and metamorphic rocks that form ranges with subdued relief

Low ranges and hills may have sharp crests. Neoproterozoic and Palaeozoic sandstone and carbonate rocks.

Sand plains, Alluvial flood plains along major rivers

ElkedraElkedra

LS 101_75 and geophysical surveys LS 101_75 and geophysical surveys are at SE end of Davenport Rangeare at SE end of Davenport Range

Palaeoproterzoic Hatches Creek Palaeoproterzoic Hatches Creek Group in spectacular foldsGroup in spectacular folds

Georgina basin rocks, Tertiary and Georgina basin rocks, Tertiary and alluvial plains to the SEalluvial plains to the SE

Awkwardness of control images Awkwardness of control images being on E edge of LS 102_75, but being on E edge of LS 102_75, but most of geophysical survey lying on most of geophysical survey lying on 101_75101_75

SummarySummary

Reports need to concentrate on successfully Reports need to concentrate on successfully more detailed aspectsmore detailed aspects

1 main physiographic and structural elements1 main physiographic and structural elements

2 major geological features - at least 3 fold 2 major geological features - at least 3 fold classificationclassification

3 sub-divisions of step 2 - may need several 3 sub-divisions of step 2 - may need several images, and data bleedimages, and data bleed

Include full spectral details of classification Include full spectral details of classification basisbasis

best criteria not always most obviousbest criteria not always most obvious