WAS SCOTLAND COVERED BY AN ICE SHEET DURING MIS4? INSIGHTS FROM THE RAISED SHORELINES OF NORTHWEST SCOTLAND

Raised shorelines provide important constraints on past sea levels, glacial isostatic adjustment, and rates and directions of vertical motion. Along northwest Scotland most raised shorelines are assumed to relate to post-Last Glacial Maximum (LGM) glacial rebound. However, rarely have these shorelines been dated. Here we present new optically stimulated luminescence (OSL) ages for a set of raised marine features at an elevation of 28 m in Slaggan Bay on Greenpoint Peninsula of Northwest Scotland. Four OSL ages suggest the feature is pre-LGM, likely marine isotope stage 3 (MIS3). Global sea levels during MIS3 are thought to be ~40-60 m below present across most of the globe. GIA models suggest that in the absence of tectonic activity, such high MIS3 shorelines across NW Scotland requires a marine isotope stage 4 (MIS4) ice sheet in Scotland with post-glacial rebound following its demise during MIS3 responsible for the elevated shoreline features at that time. These findings add to a growing body of evidence for higher sea levels during MIS3 and more ice across the northern Hemisphere during MIS4.