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 ascending order, the Hellyerian, the Tamarian, the Bernacchian and the Lymingtonian. The Epoch embraces the well-developed Tasmanian expression of the climax and retreat of the Gondwanan Late Palaeozoic glaciation, and witnesses the appearance and most prolonged development of the characteristic marine cold-water Eurydesma fauna anywhere in the world. The Hellyerian Stage, which is represented wholly by thick tillite, glaciolacustrine rhythmite clay and other glacigene rocks, is sparsely fossiliferous, but the available 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 are frequently abundant, but subordinate glacigene strata, coal measures and other freshwater rocks are also present. The basis for stage recognition rests essentially with the nature of successive marine macro-invertebrate assemblages which constitute the Eurydesma fauna, and partly, but much less importantly, with broad lithological considerations. Subsidiary microfloral data are used to supplement and complement the macrofaunal information. General lithological characters, the low to very low taxonomic diversity of faunas and floras, and palaeomagnetic data (Irving 1966). which indicate a position close to the south magnetic pole for Tasmania during Permo-Carboniferous times all consistently point to cool or cold conditions throughout the Rekunian Epoch.