Stratigraphy and depositional environments of the Wittingham coal measures, Kayuga area, Hunter Valley, New South Wales

The Kayuga area is localed near Muswellbrook in the Upper Hunter Valley of New South Wales, 150 km northwest of Newcastle. The Late Permian Wittingham Coal Measures, constituting the lower section of the Singleton Super-Group, outcrop in the area. Drilling information from coal exploration programs has formed the basis of this study. The sedimentary sequence is up to 800 m thick, and comprises coal, sandstone, claystone, and minor conglomerate and tuff. The sequence contains 22 names coal stems, which are subject to complex slitting and coalescence. Several stratigraphic units have been identified as useful marker beds. These include the Archerfield-Bulga Formation, the Wynn Tuff Band "6" (within the Upper Wynn seam), the Fairford Formation, and the Althorpe Formation. Coal seams which can be readily correlated over the area are the Edinglassie, Edderton, Upper Wynn, Bayswater, Mt Arthur, and Warkworth seams. The Archerfield-Bulga Formation separates the coal-bearing strata of the Foybrook Formation (= Vane Sub-Group) and the Jerrys Plains Sub-Group. The Archerfield-Bulga Formation was deposited as a prograding beach complex following a short, almost basin-wide marine incursion. Coarse detritus from the newly-uplifted New England Fold Belt, just east of the study area, was transported to the coast by alluvial fans and braided rivers. Isopach/facies maps and vertical profiles suggest that the Foybrook Formation was deposited in an upper delta plain environment. Facies analysis, together with isopach/facies maps and vertical profiles, indicate that the clastic sediments of the lower Jerrys Plains Sub-Group (up to Warkworth Seam) were deposited principally by meandering rivers, on an alluvial plan, Alluvial fans originating from the orogen to the east brought sediments onto the alluvial plain. The upper Jerrys Plains Sub-Group (above Warkworth Seam) is considered to have accumulated on the upper delta plain. Petrographic analysis of sandstones and conglomerates from the Archerfield-Bulga Formation and the lower Jerrys Plains Sub-Group show that the sediments are immature, feldspar-poor, lithic types, containing abundant volcanic clasts, supporting a New England Belt source.