Flora, fauna and climate of Scotland during the Weichselian Middle Pleniglacial – palynological, macrofossil and coleopteran investigations

Abstract

Thin lenses of organic-rich material, on the upper surface of a layer of glacio-fluvial deposits have been studied in an open cast coal-mine near Sourlie, western Scotland. Radiocarbon dates on antler fragments, plant debris and bulk organic matter from silt, showed that the sediments accumulated between ca. 33 500 and 29 000 14 C yr BP, during a period when this part of western Scotland was free of glaciers. The organic-rich sediments yielded a very rich flora and fauna and in total about 160 plant taxa and 61 coleopteran taxa were recorded together with other invertebrates. The Sourlie flora is one of the richest late Middle Weichselian floras yet studied within the British Isles. Leg bones of Coelodonta antiquitatis (woolly rhinoceros) and Rangifer tarandus (reindeer) were also found at the site. During this period, the landscape was treeless and the vegetation could be characterised as an intermediate between a low shrub tundra and sedge^grass^moss tundra. Both the flora and arthropod fauna suggest that during formation of the organic-rich layers at Sourlie, mean July temperatures were 9^10 ‡C. The flora suggests also that at the beginning of formation of these layers, minimum mean July temperatures increased from 7 to 9^10 ‡C, but later dropped again to 7^8 ‡C. A possible time correlation with one of the warmer periods of the Dansgaard^Oeschger cycles in the stable oxygen isotope record of the Greenland ice cores during this period is proposed. The arthropod fauna suggests that mean January temperatures were somewhere between 334 and 311 ‡C. Mean annual temperatures lay probably between 31 and 310 ‡C, which implies the possible presence of discontinuous or continuous permafrost in the area. During winter, a protective snow cover of varying thickness probably enabled perennial plants, especially shrubs, to survive. ß

Ice sheet advance, dynamics, and decay configurations: evidence from west central Scotland

“…2) (Jardine et al, 1988) following ultrafiltration pre-treatment (Jacobi et al, 2009). This age is similar to those obtained from organic remains within fully investigated interstadial profiles beneath till at Balglass ( Fig.1) (Brown et al, 2007) and Sourlie (Bos et al, 2004 Bowen et al (2002) . However, numerical modelling experiments simulate minor glacial advances into the area prior to the main sustained advance in the Late Devensian (Hubbard et al, 2009).…”

“…These lenses yielded a very rich flora and fauna deposited within a shallow pond in a treeless, low-shrub to sedge-moss tundra environment, and included bones of woolly rhinoceros and reindeer. Radiocarbon dates on antler fragments, plant debris and bulk organic matter suggest a Middle Devensian age (Bos et al, 2004).…”

Middle to Late Devensian glaciation of north‐east Scotland: implications for the north‐eastern quadrant of the last British–Irish ice sheet

“…Periods of ameliorated climate (including the Ålesund, Sandnes and Tolsta Interstadials) occurred between c. 39 ka and 29 ka, alternating with limited glacial advances in western Norway . The northern part of the last BIIS built up towards the end of MIS 3, after c. 32k a BP (Whittington and Hall, 2002;Jacobi et al, 2009) at a time when Central Scotland remained largely ice free, judging from dates of 34.5k to 28.1k cal a BP obtained on glacially over-ridden organic deposits at Sourlie (Bos et al, 2004) and Balglass (Brown, 2007) (Figure 1). Ice expanded westwards to the shelf break shortly after 30k cal a BP (Wilson et al, 2002;Scourse et al, 2009;Bradwell and Stoker, 2015a;Bradwell and Stoker, 2015b et al), it had reached at least as far as North Rona at 25-27 ka and probably over-ran St Kilda, north-west of the Western Isles (Figure 1) at this time (Hiemstra et al, 2015).…”

The northern sector of the last British Ice Sheet: Maximum extent and demise

“…The presence of these glacitectonised organic deposits constrain the onset of the last regional glaciation in Scotland to c. 31.5 ka BP (36.5 ka cal BP), because they are located close to an important conduit of the last ice sheet and they occur between two distinct tills, the lower one being weathered. A detailed re-investigation of the fossil flora and fauna at Sourlie by Bos et al (2004) produced four new conventional radiocarbon dates of between 33.3 and 29.3 ka 14 C BP, reinforcing the original findings of Jardine et al (1988). Furthermore, a reinvestigation of the organic horizon within the Tolsta Head deposits (Whittington and Hall, 2002) has yielded seven AMS dates spanning the period 31,700 ka to 26,150 14 C BP (31-37 ka cal BP), similar in age to those from Balglass and Sourlie.…”