Cambrian geology and palaeontology of the Ord Basin

The Ord Basin straddles the Northern Territory-Western Australia border and comprises from south to north the Hardman, Rosewood and Argyle Synclines. The Hardman Syncline is the most extensive of these, and preserves the most complete stratigraphic record, including Middle? Upper Cambrian Goose Hole Group and Upper Devonian Mahony Group, resting on LowerCambrian Antrim Plateau Volcanics. The Goose Hole Group consists of two subgronps, the Negri Subgroup and overlying Elder Subgroup. The Negri Subgroup includes in ascending order the Headleys Limestone, Nelson Shale, Linnekar Limestone and Panton Formation. It is predominantly a peritidal succession, with brief marine episodes represented by the Linnekar Limestone and Panton Formation (mainly between and including the Shady Camp and Corby Limestone Members in the medial part of the formation) preserving invertebrate fossils. Described from the Negri Subgroup are the trilobites Redlichia forresti (Etheridge), R. gumridgensis Laurie sp. nov., Xystridura negrina Opik and an indeterminate ptychoparioid; brachiopods Lingulella sp., Westonia sp., Kyrshabaktella mudedirri Kruse and Wimanella sp.; hyoliths Circotheca sp., Cupittheca sp., Guduguwan hardmani (Etheridge), ?Hyptiotheca sp. and an indeterminate linevitid; molluscs Latouchella accordionata Runnegar & Jell and Hampilina pintiyi Kruse sp. nov.; and an indeterminate edrioasteroid echinoderm. The Elder Subgroup comprises the Eagle Hawk Sandstone and succeeding Overland Sandstone. A variety of ichnofossils including two unnamed ichnospecies of Diplichnites, three of Monomorphichnus, one of Cruziana and Rusophycus cf. bilobatus Hall, is described from the Eagle Hawk Sandstone. The primarily peritidal nature of the Negri Subgroup limits the usefulness of the eponymous Ord Basin as a prospective stratotype for the Ordian stage. More continuously marine successions with somewhat more diverse faunas exist elsewhere in northern, central and southern Australia.