The Last Scottish Ice Sheet

Abstract

The last Scottish Ice Sheet (SIS) expanded from a pre-existing ice cap after ∼35 ka. Highland ice dominated, with subsequent build-up of a Southern Uplands ice mass. The Outer Hebrides, Skye, Mull, the Cairngorms and Shetland supported persistent independent ice centres. Expansion was accompanied by ice-divide migration and switching flow directions. Ice nourished in Scotland reached the Atlantic Shelf break in some sectors but only mid-shelf in others, was confluent with the Fennoscandian Ice Sheet (FIS) in the North Sea Basin, extended into northern England, and fed the Irish Sea Ice Stream and a lobe that reached East Anglia. The timing of maximum extent was diachronous, from ∼30–27 ka on the Atlantic Shelf to ∼22–21 ka in Yorkshire. The SIS buried all mountains, but experienced periods of thickening alternating with drawdown driven by ice streams such as the Minch, the Hebrides and the Moray Firth Ice Streams. Submarine moraine banks indicate oscillating retreat and progressive decoupling of Highland ice from Orkney–Shetland ice. The pattern and timing of separation of the SIS and FIS in the North Sea Basin remain uncertain. Available evidence suggests that by ∼17 ka, much of the Sea of the Hebrides, the Outer Hebrides, Caithness and the coasts of E Scotland were deglaciated. By ∼16 ka, the Solway lowlands, Orkney and Shetland were deglaciated, the SIS and Irish Ice Sheet had separated, the ice margin lay along the western seaboard, nunataks had emerged in Wester Ross, the ice margin lay N of the Cairngorms and the sea had invaded the Tay and Forth estuaries. By ∼15 ka, most of the Southern Uplands, the Firth of Clyde, the Midland Valley and the upper Spey valley were deglaciated, and in NW Scotland ice was retreating from fjords and valleys. By the onset of rapid warming at ∼14.7 ka, much of the remnant SIS was confined within the limits of Younger Dryas glaciation. The SIS, therefore, lost most of its mass during the Dimlington Stade. It is uncertain whether fragments of the SIS persisted on high ground throughout the Lateglacial Interstade.

Deglaciation chronology of the Donegal Ice Centre, north‐west Ireland

“…A more general implication is that all of Ireland and southern Scotland were probably completely deglaciated early in the Lateglacial Interstadial. For the British Isles as a whole, present evidence suggests that remnants of the BIIS survived the interstadial (if at all) only in the Highlands of Scotland (Finlayson et al , ; Ballantyne and Small, ).…”

Late Pleistocene sediments, landforms and events in Scotland: a review of the terrestrial stratigraphic record

“…31). The oldest known unit on the Scottish side of the border is the Chapelknowe Till Formation (McMillan et al 2011b) (Table 14), which was possibly laid down during an 'Early Advance' of Scottish ice across the Solway Firth, up the Vale of Eden and through the Stainmore Gap into eastern England (Trotter 1929;Hollingworth 1931;Trotter & Hollingworth 1932b;Evans et al 2005;Stone et al 2010;Mitchell 2013;Ballantyne and Small 2018) (Fig. 31A).…”

Examining the geometry, age and genesis of buried Quaternary valley systems in the Midland Valley of Scotland, UK

“…2018). This is in contrast to Scandinavia where pre-Quaternary deep (Brown et al 2007;Jacobi et al 2009;Ballantyne & Small 2018). Geomorphological and stratigraphical evidence suggests that glaciers initially flowed southeastwards into the area from highland sources to the northwest (Finlayson et al 2010(Finlayson et al , 2014.…”

“…; Jacobi et al . ; Ballantyne & Small ). Geomorphological and stratigraphical evidence suggests that glaciers initially flowed southeastwards into the area from highland sources to the northwest (Finlayson et al .…”