An MIS 3 age organic deposit from Balglass Burn, central Scotland: palaeo- environmental significance and implications for the timing of the onset of the LGM ice sheet in the vicinity of the British Isles

This paper reports the analysis of a glaciotectonised organic deposit located between a lower weathered till and an upper unweathered till at Balglass Burn, north of the Campsie Fells in central Scotland, UK, close to the centre of ice accumulation in Scotland. Sedimentology, pollen, macroscopic plant remains and Coleoptera indicate accumulation in a small pond, as part of an open, tundra landscape with low floral diversity. MCR palaeotemperature reconstructions for the Coleoptera give a mean temperature for the warmest and the coldest months of 8 to 108C and 26 to 108C respectively, indicating the presence of at least discontinuous permafrost. Six AMS dates on Carex fruit and Coleoptera fragments give ages between 34 480 and 28 050 14C yr BP (ca. 39.8 to
ca. 32.8 cal. yr BP; Fairbanks et al. (2005)). The upper till and the glaciotectonism are attributed to glaciation during the LGM. Glaciotectonic deformation means that the ages do not indicate sequential development and it is not possible to relate this palaeo-evidence to the fine resolution palaeoclimatic signature for MIS 3. However, the fact that this part of central Scotland was ice-free at this time means that some recent proposals suggesting that the British ice sheet began to accumulate around the middle of MIS 3 are unlikely to be correct.