Reconstruction of the Oligocene vegetation at Pioneer, northeast Tasmania

Abstract

The Oligocene vegetation at Pioneer was closed temperate rainforest dominated by Nothofagus johnstonii Hill, which probably produced N. menziesii-type pollen. However, other angiosperms (Quintinia, Cupaniae, Ilex, Cunoniaceae, Myrtaceae, Proteaceae and Winteraceae) were also present, as well as several conifers (Athrotaxis, Phyllocladus, Podocarpus, Dacrydium, Dacrycarpus and Araucariaceae). This rainforest was floristically more complex that the modern Tasmanian Nothofagus cunninghamii rainforests but contained many taxonomically related elements. One major difference was that a fern similar to extant Cyathea filled the riparian niche now largely occupied by the tree-fern Dicksonia antarctica. There is indirect evidence that species producing Nothofagus brassii-type pollen may have occurred upstream of the site of deposition, suggesting that the Nothofagus species were altitudinally zoned or edaphically restricted. The current absence of many of these Nothofagus species in Tasmania may be due to their inability to survive the low temperatures of the Quaternary glaciations. The high degree of similarity of the Pioneer palynoflora to that recorded in Oligocene sediments in onshore (Partridge, 1971) and offshore (Stover & Partridge, 1973; Stover & Evans, 1973) Gippsland Basin strongly suggests that there was little regional differentation in southeastern Australia at that time.