Cretaceous and early Tertiary climates of Antarctica: evidence from fossil wood

Abstract

Fossil wood is abundant in Cretaceous and early Tertiary sediments of the northern Antarctic Peninsula region. The wood represents the remains of vegetation that once grew in high palaeolatitudes when the polar regions were warmer, during former greenhouse climates. Fossil wood is a unique data store of palaeoclimate information. Analyses of growth rings and anatomical characters in fossil wood provide important information about temperature, rainfall, seasonality and climate trends for this time period in Antarctica. Climate signals from fossil wood, supported by sedimentary and geochemical evidence, indicate a trend of cool climates during the Early Cretaceous, followed by peak warmth during the Coniacian to early Campanian. Narrower growth rings suggest that the climate cooled during the Maastrichtian and Palaeocene. Cool, wet and possibly seasonal climates prevailed at this time, with tentatively estimated mean annual temperatures (MATs) falling from 7°C to 4–8°C respectively, determined from dicotyledonous (dicot) wood anatomy. The Late Palaeocene/Early Eocene was once again warm, with estimated MATs of 7–15°C from dicot wood analysis, but conditions subsequently deteriorated through the latter part of the Eocene, when cold seasonal climates developed, ultimately leading to the onset of Cenozoic ice sheets and the elimination of vegetation from most of Antarctica.