central Australian Project Lecture 15

Main geological elements Palaeoproterozoic and Mesoproterozoic cratons - granitoids, gneiss, schist Palaeoproterozoic and Mesoproterozoic cratons - granitoids, gneiss, schist Neoproterozoic to late Paleozoic sedimentary basins Neoproterozoic to late Paleozoic sedimentary basins Tertiary weathering and sedimentary plains; some extensive dune fields Tertiary weathering and sedimentary plains; some extensive dune fields Alluvial outwash adjacent to rivers Alluvial outwash adjacent to rivers

Arunta Block & Amadeus Basin

Arunta Block Extensive c Ma sediments and volcanics Extensive c Ma sediments and volcanics High-grade metm, defm, granite at c Ma High-grade metm, defm, granite at c Ma Uplift, re-exposure before Ma Reynolds Range-Hatches Creek Groups Uplift, re-exposure before Ma Reynolds Range-Hatches Creek Groups High-grade metm and defm at c Ma, 1580 Ma High-grade metm and defm at c Ma, 1580 Ma Southern Arunta - different Ma gneiss defm metm, joined to rest at c Ma Southern Arunta - different Ma gneiss defm metm, joined to rest at c Ma

Musgrave Block C.1550 and 1300 Ma protoliths to high- grade gneiss C.1550 and 1300 Ma protoliths to high- grade gneiss Granulite faces events at c. 1300, 1200 Ma with extensive felsic magmatism Granulite faces events at c. 1300, 1200 Ma with extensive felsic magmatism C Ma Giles Complex and extensive volcanism on western end of block C Ma Giles Complex and extensive volcanism on western end of block 1000 and 800 Ma dykes 1000 and 800 Ma dykes C. 550 ma Petermann Orogeny C. 550 ma Petermann Orogeny

Amadeus & Georgina Basins Neoproterozoic basins abundant in Australia Neoproterozoic basins abundant in Australia Mostly weakly deformed, except in Adelaide foldbelt Mostly weakly deformed, except in Adelaide foldbelt Inconsistent mostly shallow marine sedimentation from c. 900 Ma to Devonian Inconsistent mostly shallow marine sedimentation from c. 900 Ma to Devonian Sandstone, siltstone, carbonate dominate Sandstone, siltstone, carbonate dominate Depo-centres changed with time Depo-centres changed with time Current basin margins have little to do with deposition, mostly related to deformation at c. 550 Ma (south Amadeus), Ordovician and Devonian (north Amadeus, Georgina) Current basin margins have little to do with deposition, mostly related to deformation at c. 550 Ma (south Amadeus), Ordovician and Devonian (north Amadeus, Georgina) Exposed Georgina dominated by Cambrian silts Exposed Georgina dominated by Cambrian silts

Cretaceous and Tertiary High sea-levels, craton subsidence lead to much of inland eastern Australia covered by shallow seas in Mesozoic periods (J, K) High sea-levels, craton subsidence lead to much of inland eastern Australia covered by shallow seas in Mesozoic periods (J, K) Sediments later concentrate opal and dinosaur fossils, inland gas fields Sediments later concentrate opal and dinosaur fossils, inland gas fields Tertiary - intense weathering to form duricrusts and ferricrusts, now exposed as breakaways Tertiary - intense weathering to form duricrusts and ferricrusts, now exposed as breakaways Western side of GA basin lower than east - bubbler springs Western side of GA basin lower than east - bubbler springs

Specifics - Alice Scene and geophysical surveys straddle the northern margin of the Amadeus Scene and geophysical surveys straddle the northern margin of the Amadeus Need structural diagram and then simple 3 fold classification (Arunta, Amadeus, clay) Need structural diagram and then simple 3 fold classification (Arunta, Amadeus, clay) Basement stratigraphy dominated by separating granite batholiths, metaseds etc, ?mafic dykes Basement stratigraphy dominated by separating granite batholiths, metaseds etc, ?mafic dykes

Physiography 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

Elkedra LS 101_75 and geophysical surveys are at SE end of Davenport Range LS 101_75 and geophysical surveys are at SE end of Davenport Range Palaeoproterzoic Hatches Creek Group in spectacular folds Palaeoproterzoic Hatches Creek Group in spectacular folds Georgina basin rocks, Tertiary and alluvial plains to the SE Georgina basin rocks, Tertiary and alluvial plains to the SE Awkwardness of control images being on E edge of LS 102_75, but most of geophysical survey lying on 101_75 Awkwardness of control images being on E edge of LS 102_75, but most of geophysical survey lying on 101_75

Summary Reports need to concentrate on successfully more detailed aspects Reports need to concentrate on successfully more detailed aspects 1 main physiographic and structural elements 2 major geological features - at least 3 fold classification 3 sub-divisions of step 2 - may need several images, and data bleed Include full spectral details of classification basis Include full spectral details of classification basis best criteria not always most obvious best criteria not always most obvious