The Mt. Daubeny Formation: arenite-rich ?Late Silurian-Early Devonian (Gedinnian) strata in far western New South Wales. and Addendum

Abstract

The 6 km-thick, nonmarine Mt Daubeny Formation, commonly pale-red in colour, crops out in far western New South Wales. It is largely composed of arenite with subordinate siltstone and rudite. A basal orthoquartzite, the Koonburra Creek Quartzite Member, is present in the south whereas in the north three horizons (~ 0.5 km, 2.5 km and ~4.5 km above basement) contain andesite flows. The central part of the outcrop contains common 6m-thick orthoquartzite beds which are interbedded largely with pale-red or grey arenite and siltstone. The sequence containing orthoquartzite beds is at least 775m thick in che west and it is ~ 690m thick in the east where it is overlain by a ~610m sequence composed of brownred arenite and siltstone.The upper part of the formation is Early Devonian (Gedinnian) in age, is dated by fossil plants. The base of the formation is probably ~ 4 m.y. older than the fossiliferous horizon and this basal part may be latest Silurian in age. An unknown thickness of the formation has been removed by erosion since it was deposited.Palaeocurrents indicate that during the ?Latest Silurian-Early Devonian a mountainous terrain composed largely of Precambrian -? Cambrian rocks lay west of the present outcrop area of the formation area and provided the sediment from which the formation was formed.