Peat bank growth, Holocene palaeoecology and climate history of South Georgia (sub-Antarctica), based on a botanical macrofossil record N. Van der Putten a, d, * , C. Verbruggen a , R. Ochyra b , S. Spassov c , J.-L. de Beaulieu d , M. De Dapper a , J. Hus c , N. Thouveny e a Geography Department, Ghent University, Krijgslaan 281, S8/B2, B-9000 Ghent, Belgium b Laboratory of Bryology, Institute of Botany, Polish Academy of Sciences, Ul. Lubicz 46, PL-31-512 Cracow, Poland c Section du Magne ´tisme Environnemental, Centre de Physique du Globe de l’Institut Royal Me´te´orologique de Belgique, B-5670, Dourbes (Viroinval), Belgium d IMEP, CNRS UMR 6116, Universite´ Paul Ce ´zanne, Europo ˆle Me ´diterrane ´en de l’Arbois, Ba ˆtiment Villemin, Avenue Philibert BP 80, F-13545 Aix-en-Provence Cedex 04, France e CEREGE, Europo ˆleMe´diterrane ´en de l’Arbois, BP 80, F-13545 Aix-en-Provence Cedex 04, France article info Article history: Received 1 August 2007 Received in revised form 18 September 2008 Accepted 20 September 2008 abstract Botanical macrofossil analysis of a more than 9000 years old, radiocarbon dated peat sequence of a moss peat bank from South Georgia, shows a clear evolution in the vegetation. Seven ecological phases could be distinguished and they can be interpreted in terms of climate development during the Holocene. Until 2200 years ago, Warnstorfia fontinaliopsis was the dominant moss species pointing to a wet environment. Lower numbers of this species in association with the presence of drier species are assumed to indicate drier periods, such as occurring between ca 6000–5200 and 4400–3400 cal yr BP. The most prominent and definitive vegetation change took place around 2200 cal yr BP. A Polytrichum–Chorisodontium moss peat bank was formed, which is still growing there today. The forcing mechanism for this vegetation change is thought to be a temperature decrease, rather than a precipitation decrease. This conclusion is mainly based on the fact that, today, moss peat banks have their optimal occurrence range in the maritime Antarctic, a region were the mean annual temperature is ca 4  C lower than on South Georgia. The remarkable change in the moss bank vegetation at 2200 cal yr BP raises the question whether this moment was only a short climatic deterioration, or a definitive change to a cooler and wetter climate after a Holocene climatic optimum period. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction For the past decades, climatic connections between the northern and southern hemisphere and the driving mechanism behind these have been important issues in research on past climate and environmental change (Bard et al., 1997; Denton et al., 1999; Blunier and Brook, 2001; Steig and Alley, 2002). This research is mainly based on data from the last glacial period and glacial– interglacial transition. Evidence from ice cores showed an asyn- chronous pattern of climate change in the Antarctic and the Northern Hemisphere (Blunier et al., 1998). However, other palae- oclimatic records from southern, mid and low latitudes provided evidence for synchronic climate change with the north Atlantic region during the last glacial–interglacial transition (Ariztegui et al., 1997; Bard et al., 1997). In this context, the Polar Frontal Zone (PFZ), a major climatic and oceanic boundary in the Southern Ocean, has been brought forward as the boundary between Antarctica’s climate and that of the rest of the world (Broecker, 1996; Bard et al., 1997; Domack and Mayewski, 1999). The region that is charac- terised by the PFZ is called the sub-Antarctic (ca 44  –55  S, Fig. 1). Palaeoclimatological records from mid and high southern lati- tudes are scarce compared to the data available from the same latitudes in the northern hemisphere, especially for the Holocene. Terrestrial records from maritime and continental Antarctica (Fig. 1) were reviewed by Ingo ´ lfsson et al. (1998) and Hodgson et al. (2004), and several papers on marine records have been published during the last decade. While most of these marine cores are sit- uated in the Antarctic Peninsula region or near the coast of the Antarctic continent, only a few are situated in the area of the PFZ (Hodell et al., 2001; Nielsen et al., 2004). The terrestrial part of the sub-Antarctic consists of only six islands or island groups, dispersed in the vast Southern Ocean, which makes them an interesting source for palaeoenvironmental and -climatological data. More * Corresponding author. Geography Department, Ghent University, Krijgslaan 281, S8/B2, B-9000 Ghent, Belgium. Tel.: þ32 9 264 4701; fax: þ32 9 264 4985. E-mail address: nathalie.vanderputten@ugent.be (N. Van der Putten). Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev 0277-3791/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2008.09.023 Quaternary Science Reviews 28 (2009) 65–79