Ammonoids and the correlation of the Lower Carboniferous rocks of eastern Australia

The occurrence of ammonoids in the Lower Carboniferous rocks of eastern Australia is reviewed within a biostratigraphic framework provided by the brachiopod zones that have been summarized most recently by Jones & Roberts (1976). Ammonoid abundance is low at all stratigraphic levels. Nowhere are more than 20 specimens known at a locality, and usually there are only one or two. The group is too sparse to be used for local or regional correlation, and its main value is for the intercontinental correlation of a number of well separated horizons. The rocks dated range in age from middle Tournaisian (Tn_2a) to late Visean V_3c). Some relatively minor differences between ammonoid and conodont ages remain to be resolved. The biogeography is briefly discussed.

The type specimens of all available previously described species have been examined and where necessary they are re-illustrated. New species described are Irinoceras tuba, Muensteroceras jenkinsi, M. delepinei, M. merlewoodense, Beyrichoceras mackellari, B. bootibootiense, Nomismoceras pseudocyclus, Goniatites mundubberensis, G. cuniculus, Protocanites careyi, and Cantabricanites jelli. Several species that are probably new are described under open nomenclature.