A lacustrine record of the Pleistocene–Holocene boundary in southernmost Greenland KARL LJUNG 1 and SVANTE BJÖRCK 1 Ljung, K. & Björck, S., 2004: A lacustrine record of the Pleistocene–Holocene boundary in southernmost Greenland. GFF, Vol. 126 (Pt. 3, September), pp. 273–278. Stockholm. ISSN 1103-5897. Abstract: A sediment core from a lake in the Kap Farvel area on South Greenland was analysed with respect to pollen and microfossil content, loss-on-ignition, magnetic susceptibility and radiocarbon age. The aim was to reconstruct the limnic and terrestrial changes taking place at the Pleistocene–Holocene boundary. Organic sedimentation started between 12200 and 12800 cal yr B.P. Break-up of sea-ice around Kap Farvel, as indicated by the appearance of marine dinoflagellates (Hystrix), took place some hundred years after the transition into Preboreal. The pollen analysis indicates that the area was barren during the Younger Dryas and that the Holocene vegetation establishment was slightly delayed. Keywords: Pleistocene–Holocene boundary, pollen analysis, environmental changes, Kap Farvel, South Greenland. 1 GeoBiosphere Science Centre, Department of Geology, Quaternary Sciences, Lund University, Sölveg. 12, SE-223 62 Lund, Sweden; karl.ljung@geol.lu.se Manuscript received 23 October 2003. Revised manuscript accepted 1 July 2004. Introduction The Pleistocene–Holocene transition was a time of significant climate change around the North Atlantic (e.g. Koç et al. 1993; Peteet et al. 1994; Rundgren 1995; Björck et al. 1998). On Greenland this change has been recorded in different deep ice core records, and for example, the combined bore hole temperature profile and the δ 18 O values of the ice as well as other techniques imply that areas around sea level in Greenland experienced a mean annual temperature rise at the end of the Younger Dryas stadial in the order of 15–20°C (Johnsen 1995; Cuffey 1997; Severinghaus 1998). Until recently the terrestrial record from Greenland only extended back to the early Holocene (Fredskild 1973; Funder 1978), and climatic information from such records during the Younger Dryas and the following transition was lacking. However, in 1999 pre-Holocene records were found on islands between Nanortalik and Kap Farvel in southernmost Greenland (Fig. 1) and their late-glacial age were confirmed by several 14 C dates (Bennike & Björck 2000; Björck et al. 2002). One aim of these studies was to reconstruct the first late-glacial sea level curve from Greenland (Bennike et al. 2002) and another objective was to reconstruct the pre-Holocene regional climatic development by detailed analyses of the oldest lake sediment sequence found in the region. This is found on the island of Angissoq, 30 km south of Nanortalik (Fig. 1), and a multi-proxy study of a lake sediment core (N14) shows that the Younger Dryas seems to have been characterised by a fairly arid climate compared to today with cold winters and mild summers (Björck et al. 2002). In connection with the 1999 field work, several lake records were found to cover the Younger Dryas–Preboreal transition and in one of these, lake N23 on the Taterakasik peninsula 20 km south-east of Nanortalik (Fig. 1), this transition has been studied with respect to sediment lithology and the content of pollen, spores, different types of algae and organic matter. This was combined with measurements of magnetic susceptibility and 14 C datings. The aim of the study is to interpret and discuss the Younger Dryas–Preboreal development of terrestrial vegetation and limnic environment, and to place the development within a regional context. Description of the study site Lake N23 is situated on the Taterakasik peninsula at 47 metres above mean sea level (m a.s.l.). The peninsula is about 4 km long and 2 km wide, and the highest point reaches 244 m a.s.l. Although the exact local marine limit is not known, several independent indications imply that it is situated 30–40 m a.s.l. (Bennike et al. 2002). The lake is 100 m long, 200 m wide and 2.2 meters deep, and drains to the north through a small gulch. The surroundings are characterised by Precambrian gneiss bedrock. Patchy occurrences of till and a few perched boulders are found in the immediate surrounding. The vegetation on the peninsula is dominated by dwarf-shrubs, Empetrum, Vaccinium and Salix. Methods The lake was cored from winter ice in the spring of 1999 (Bennike & Björck 2000). Two parallel cores were taken with a 75 mm diameter Russian-corer with a 1 m long chamber from the GFF volume 126 (2004), pp. 273–278. Article