Paleocene forests and climates of Antarctica: signals from fossil wood

During the green house world of the Paleocene, Antarctica was covered in extensive forests, even though the continent was situated over the South Pole. Fossil wood is abundant in the marine sequences of Seymour Island, Antarctica. Originating from forests that once grew on a volcanic arc now represented by the Antarctic Peninsula. This research presents a detailed study of the forests and climates of Antarctica primarily using a new assemblage of fossil wood and palynomorphs, directly tied to a sedimentary sequence (K/Pg boundary to Late Paleocene in age) on Seymour Island, which has allowed for a more rigorous interpretation of the composition and structure of the Antarctic Peninsula forests and the climates under which they grew. Tree types identified from fossil wood include: Agathoxylon, Phyllocladoxylon, Protophyllocladoxylon, Podocarpoxylon/Cupressinoxylon, Nothofagoxylon, Weinmannioxylon, Myrceugenelloxylon and Antarctoxylon. Their nearest living relatives (NLR) are found growing in warm to cool temperate Southern Hemisphere forests. Palynomorphs revealed diverse Podocarpaceae including Lagarostrobos franklinii (Phyllocladidites mawsonii) and shrubby angiosperm taxa such as Proteaceae, as well as ferns and mosses. Collective analysis of taxomomy, wood preservation, sedimentology and NLRs indicate that the lowland forests were similar to the cool temperate mixed Nothofagus forests of New Zealand and Thamnic/Implicate forests in Tasmania. Upland floras may have resembled Araucaria – Nothofagus woodlands found in cool temperate Chile today. Coexistence Analysis indicates marginally warm to cool temperate climates with sufficient rainfall for tree growth. Analysis of angiosperm anatomy suggests sufficient water availability. Mean growth ring analysis suggests a trend towards cooler climates from the Early to the Late Paleocene. However, the majority of trees suggest growth under a fluctuating climate. For the first time specific gravity (SG) has been calculated for fossil wood from Antarctica and has provided further insight into the ecology and growth conditions of the trees. Narrow values of SG (0.50 – 0.80) are indicative of a temperate climate in the Paleocene of Antarctica.