ECOLOGY OF PALEOCENE-EOCENE VEGETATION AT KAKAHU, SOUTH CANTERBURY, NEW ZEALAND

A plant-fossil bearing sequence at Kakahu, south Canterbury, New Zealand, probably extends from the late Paleocene to the Early Eocene (palynological Zones PM3-MH1). One of the leaf macrofossil assemblages previously published from this locality as Paleocene (J38/f58), is here regarded as coming from very close to, and probably just above the Paleocene - Eocene boundary. Palynology indicates there was a major change in vegetation throughout the Kakahu sequence from conifer to angiosperm (possibly Casuarinaceae) dominance, which is similar to elsewhere in New Zealand. In this study a palynological "interzone" is identified that separates these two extremes. It may correspond to rapid vegetation-climate change over the Paleocene-Eocene boundary. Fossil leaf cuticle is of low diversity, but includes locally common Podocarpaceae conifers, Gnetaceae, at least four species of Lauraceae, and a possible Aquifoliaceae. An important conclusion based on the presence of ubiquitous charcoal is that there was significant landscape burning throughout the sequence. This is likely to reflect climatic conditions but also the character of the vegetation, as controlled by soil conditions, may be implicated. It is consistent with studies in the Northern Hemisphere, which also find significant charcoal around the Paleocene-Eocene boundary. Using leaf margin relationships based on Australian rainforests, the mean annual temperature for two previously published assemblages is remarkably cool - around 4-8 degrees C although leaf size suggests warmer conditions, perhaps around 12-20 degrees C.