A fossil wood flora from King George Island: ecological implications for an Antarctic eocene vegetation

Abstract

Early Tertiary sediments of the Antarctic Peninsula region continue to yield a rich assemblage of well-preserved fossil dicotyledonous angiosperm wood. The wood flora under consideration is from the Collins Glacier region on Fildes Peninsula, King George Island and is derived from tuffaceous sediments of the Middle Unit of the Fildes Formation. These deposits accumulated in a volcanic setting adjacent to a basic-intermediate stratocone. The fossil assemblage provides further evidence for the existence of cool temperate forests, similar in composition to those found today in New Zealand, Australia and, in particular, southern South America. This paper describes two conifer and five angiosperm morphotypes, four of which are new additions to the Antarctica palaeoflora records. Cupressinoxylon Goeppert, which is the dominant conifer in terms of numbers, and Podocarpoxylon Gothan represent the conifers. The angiosperm component includes two species of Nothofagoxylon and two previously undescribed wood morphotypes that exhibit greatest anatomical similarity to woods of Luma A. Gray (Myrtaceae) and Eucryphia Cav. (Cunoniaceae). These morphotypes are described and assigned to the organ genera Myrceugenelloxylon Nishida, and Weinmannioxylon Petriella, respectively. A model based on the extant cool temperate Valdivian rainforests is proposed and ecological reconstructions based on palaeobotanical and geological evidence suggest that changes in the palaeovegetation reflect natural dynamics following volcanic disturbances.