WESTERN AUSTRALIAN DIVISION
West Australian Geologist (WAG)
Bi-monthly newsletter of the Western Australian Division of the Geological Society of Australia Inc.
Number 500: April ̶ May 2013 (4.1 Mb PDF file)
Time: 5.30 pm for 6.00 pm formal start (bar open upstairs before talk)
Venue: Irish Club of WA,
NEXT MONTHLY MEETING
Wednesday 1st May, 2013
Talk title: The Petermann Orogeny: syn-tectonic sediment pulse across the Centralian Superbasin and beyond traced by detrital zircon ages and Lu–Hf isotopes
Speaker: Peter Haines, Geological Survey of Western Australia, 100 Plain Street, East Perth WA 6004
Abstract: The late Neoproterozoic to early Cambrian (c. 580–530 Ma) Petermann Orogeny of central Australia uplifted the Mesoproterozoic Musgrave Province, supplying immature siliciclastic detritus to adjacent remnants of the Centralian Superbasin, including the Amadeus Basin to the north. Previous work identified the Mount Currie Conglomerate (Kata Tjuta/Mt Olga) and Mutitjulu Arkose (Uluru/Ayres Rock) as proximal syn-Petermann deposits, with the Arumbera Sandstone of the northeastern Amadeus Basin as a distal deltaic equivalent. This left an inexplicable absence of syn-Peterman deposits across the central and western Amadeus Basin.
Revised regional correlations, and paleocurrent and sedimentological observations in the west and southwest Amadeus Basin suggest that syn-Petermann deposits are much more extensive and thicker than previously thought. Syn-Petermann deposits include the Winnall beds, Carnegie Formation, Ellis Sandstone, Sir Frederick Conglomerate, Maurice Formation, Angas Hills beds, and some outcrops previously mapped as Ligertwood beds. The basal unconformity of the Winnall beds (and by new correlation, Carnegie Formation) was previously interpreted as evidence for a separate pre-Petermann tectonic event (‘Souths Range Movement’), but is here correlated with the onset of the Petermann Orogeny. A younger angular unconformity between the Winnall beds and late Petermann-aged Mount Currie Conglomerate in the Northern Territory may correlate with a newly recognised angular unconformity in Western Australia.
A Musgrave sediment source for these deposits is confirmed by detrital zircon ages and Lu–Hf isotopic signatures. The dominant detrital zircon ages are around 1220–1150 Ma (the age of Musgrave Orogeny felsic intrusives), with minor contributions correlated with the Giles Event (1085–1040 Ma), Mount West Orogeny (1345–1293 Ma), and older events.
A review of detrital zircon age data for late Neoproterozoic to early Cambrian siliciclastics in the Officer Basin shows a very similar age spectrum to that of the syn-Petermann deposits in the Amadeus Basin. Interestingly, these deposits include thick eolian intervals, a facies not recognised in the north. One possibility is that the orogenic mountain belt had a rain shadow on the southern side. Further afield, detrital zircon datasets suggest a syn-Petermann sediment contribution to the Georgina (NT) and Murraba (WA/NT) Basins, and the Adelaide Rift Complex (SA).
About the speaker: Peter Haines holds BSc (Hons) and PhD degrees from the University of Adelaide. He has worked for the Northern Territory Geological Survey, Universities of South Australia, Adelaide and Tasmania, and is currently with the Basins and Energy Geoscience group at the Geological Survey of Western Australia.
Gibb Maitland Medal
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