Conodonts, Corals and Stromatoporoids from Subsurface Lower Devonian in the Northparkes Porphyry District of Central Western New South Wales and their Regional Stratigraphic Implications

Abstract

Documented in this report is a small fauna recovered from an unnamed stratigraphic unit of bioclastic limestone, black shale and carbonaceous mudstone intersected in a drill hole (NPM-GD871) undertaken by CMOC-Northparkes Mines in the Northparkes porphyry district, located ca 30 km NW of Parkes, central western New South Wales. It includes six conodont species (Panderodus unicostatus, Pandorinellina exigua, Pelekysgnathus sp., Wurmiella excavata, Zieglerodina remscheidensis and gen. et sp. indet.), one rugose coral (Microplasma ronense), three tabulate coral species (Favosites duni, Squameofavosites bryani and Thamnopora minor) and one stromatoporoid species (Densastroma sp.). Faunal analysis indicates a maximum age of late Lochkovian and a minimum age of Pragian for this unit, equivalent to the upper part of the Derriwong Group. The fauna is also comparable with those recovered from the Jerula Limestone Member of the Gleninga Formation (upper part of the Yarra Yarra Creek Group) exposed farther west. Conodont data documented here suggest that the base of the Derriwong Group is diachronous across the region, and on the eastern flank of the Tullamore Syncline has a minimum age of the late Pragian rather than early Lochkovian as currently accepted.