The Triangle Group exposed along Triangle Creek, near Rockley, New South Wales, consists of two thick siltstone-chert units enclosing a 1200 m thick mafic volcanic-derived feldspathic arenite unit. The latter unit represents an eastern extension of the Ordovician volcaniclastic apron derived from the Molong Volcanic Rise. The feldspathic arenite unit cannot be traced farther south than Mt Lawson. A chert collected 50 m above the top of the feldspathic arenite unit, in Triangle Creek, has yielded a conodont fauna that suggests a late Darriwilian to early Gisbomian age. The upper siltstone-chert unit is older than graptolitic Triangle Group shales in the Taralga area, and may correlate with the lower part of the Warbisco Shale of the Bendoc Group, or the upper parts of Adaminaby Group. The Rockley Volcanics along Triangle Creek are Eastonian or older and correlate with the Sofala Volcanics. A submarine basic volcanic eruptive event is therefore indicated at this time in the Rockley district. The (7)Rockley Volcanics near the Isabella River, south of Burraga, are significantly younger than the Rockley Volcanics along Triangle Creek.
- New South Wales
- Triangle group
ASJC Scopus subject areas
- Earth and Planetary Sciences (miscellaneous)
- Earth and Planetary Sciences(all)