Biostratigraphic nomenclature for Late Palaeozoic rocks in Tasmania

Abstract

The Rekunian Series is proposed for part of the Late Palaeozoic (Stephanian-Kazanian Stages) of Tasmania. It is divided into four stages which are, in ascendingorder, the Hellyerian, the Tamarian, the Bernacchian and the Lymingtonian. The Epochembraces the well-developed Tasmanian expression of the climax and retreat of theGondwanan Late Palaeozoic glaciation, and witnesses the appearance and most prolongeddevelopment of the characteristic marine cold-water Eurydesma fauna anywhere in theworld.The Hellyerian Stage, which is represented wholly by thick tillite, glaciolacustrinerhythmite clay and other glacigene rocks, is sparsely fossiliferous, but theavailable evidence indicates that it pre-dates the appearance of both Eurydesma and Glossopteris.The Tamarian, Bernacchian and Lymingtonian Stages are mostly represented by shallow-water marine deposits in which glacially derived dropstones arefrequently abundant, but subordinate glacigene strata, coal measures and other freshwaterrocks are also present. The basis for stage recognition rests essentially withthe nature of successive marine macro-invertebrate assemblages which constitute the Eurydesma fauna, and partly, but much less importantly, with broad lithologicalconsiderations. Subsidiary microfloral data are used to supplement and complementthe macrofaunal information.General lithological characters, the low to very low taxonomic diversity offaunas and floras, and palaeomagnetic data (Irving 1966). which indicate a positionclose to the south magnetic pole for Tasmania during Permo-Carboniferous times allconsistently point to cool or cold conditions throughout the Rekunian Epoch.