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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) Monthly Meetings Time:
5.30 pm for 6.00 pm
formal start (bar open upstairs before talk) Venue: Irish Club of WA, Download a map showing the
location, or check out the venue with Google
Maps. 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 Guidelines download: MS
Word doc Last modified: 22
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