The geology of the Yarrol Region. - Part 1, Biostratigraphy

In the eastern part of the Yarrol Basin, an uninterrupted sequence of marine beds ranging in age from Upper Devonian to Lower Permian (Sakmarian) is exposed around the north-plunging Yarrol Syncline. Prolific faunas occur throughout and more than 100 species have been identified. Of these twenty-three are new species and are described below. They include Schizodus ellioti, S. minutus, S. globosus, Oriocrassatella compressa, Limipecten burnettensis, L. multistriatus, Promytilus cancellatus, Myonia pollocki, Nuculana etheridgei, Sanguinolites gracilis, Neoplatyteichum dickinsi, Pseudobaylea poperimensis, Planikeeneia pristina, Montospira montoensis, Spiriferellina australis, Punctospirifer ambiguus, Tylothyris multicostatus, Alispirifer contractus, A . laminosus var. transversus, Booralia burnettensis, Neospirifer campbelli, Cancrinella levis, Lissochonetes yarrolensis. Existing species which have been identified in the faunas are recorded and figured. Different taxonomic groups are dominant at various levels in the succession, viz. Upper Devonian-solitary rugose corals and plants; Lower Carboniferous (Tournaisian)-spiriferid brachiopods, gastropods; L. Carboniferous (Visean)-spiriferid and productid brachiopods, solitary rugose corals; Lower Carboniferous (Namurian)-spiriferid brachiopods; Middle Carboniferous-productid and punctate spiriferid brachiopods, fenestellid bryozoans; Upper Carboniferous-pelecypods and gastropods; Lower Permian (early Sakmarian)-Eurydesma and other molluscs; Lower Permian (late Sakmarian)-brachiopods and fenestellid bryozoans. Many of the species are long ranging and strongly influenced by facies, so that we find the succession of faunal types listed above corresponding fairly well with a changing lithological sequence.