Woodgreen, Northern Territory : explanatory notes
Northern Territory Geological Survey
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Geology; Georgina Basin; Arunta Region
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Australia 1:100 000 Geological Map Series
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Northern Territory Government
4 suggesting that it may be restricted to a zone east of the main ranges in northern Woodgreen. The Oorabra Arkose is interpreted as a fluviatile unit, deposited during the waning phase of the glacial episode responsible for deposition of the Boko Formation, probably at about 600 Ma. Evidence for glacial influence is twofold: the local presence of faceted and striated cobbles in HUCKITTA and the widespread evidence of minimal chemical weathering, consistent with very cold conditions. Ediacaran Mopungagroup The term Mopunga Group has had a complex history of usage. As most recently redefined by Kruse in Dunster etal (2007), the group is an unconformitybounded package, comprising the GnallanaGea Arkose and Elyuah, Grant Bluff, Elkera, Central Mount Stuart and Andagera formations. Only the Elyuah, Grant Bluff and Central Mount Stuart formations are mapped in Woodgreen, although a correlative interval to the Elkera Formation can be recognised within the Central Mount Stuart Formation, based on drillcore data. Smith (1964) included the Mount Baldwin Formation (HUCKITTA) within the Mopunga Group, but this unit was subsequently removed by Walter (1980), based on the recognition of a local basal unconformity and the presence of Cambrian trace fossils. However, field comparisons between Neoproterozoic strata in HUCKITTA and Woodgreen suggest that some outcrops mapped as Mount Baldwin Formation (including all or most of the type section) are likely to be laterally equivalent to parts of the Central Mount Stuart Formation and thus, should be included in the Mopunga Group. Elyuah Formation (LPel) The Elyuah Formation was defined in HUCKITTA (Smith 1964, Walter 1980, Freeman 1986) and was previously recognised in the Woodgreen area by Walter (1980), based on drillcore information. The formation has been intersected in the subsurface in diamond drillholes CMS to 4. The thickest intersection of 94 m is in CMS2 (437.5531.4 m Figure15. Oorabra Arkose. Coarse massive arkose (behind hammer) overlain by sharpbased, channelised cobble conglomerate. Hammer (lower half of photo, just right of centre) for scale. 432780mE 7551039mN, 4 km SE of New Bore. Figure16. Crudely polished and coarsely ridged unconformity surface, interpreted as a possible glaciated surface, between Utopia Quartzite(?) and overlying Oorabra Arkose. 431655mE 7552292mN, 2.5 km ESE of New Bore.
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