Sea-level changes in Scotland during the last 18,000 years†

At the Devensian glacial maximum, around 18,000 BP, the surface of the sea intersected the continental shelf west of the present Scottish mainland and in the North Sea area sea-level probably stood at around -60 m O.D. Broadly, during deglaciation relative sea-levels at first were lower than O.D., shorelines being positioned at sites now located offshore. Later, relative sea-levels were markedly higher than O.D., the corresponding shorelines being positioned at sites now located inland; in the east the Late Devensian marine limit is around +50 m O.D., in the west around +41 m O.D. Rapid changes in the positions of relative sea-level may have occurred occasionally, e.g. shortly after formation of the `Main Perth Shoreline' and around the time of the Loch Lomond Readvance. Time-elevation graphs and sea-level curves are based on index ‘points’ whose time ranges are defined by the standard deviations from the mean radiocarbon ages of dated samples and whose ‘derived elevations’ differ from measured elevations by values determined by parameters such as former tidal range and the depth range of a marine organism that provided dated shell material. Sea-level curves for the western part of the Forth valley, the northern seaboard of the Solway Firth, the Oban-Lorne, Lochgilphead and Ardyne areas of Argyll, and Lower Strathearn illustrate variations in relative sea-level positions during Late Devensian and Holocene times that are consistent with global changes of sea-level occurring in conjunction with land movements during and following deglaciation. Shoreline studies, leading to construction of isobases for the ‘Main Perth’, ‘Main Lateglacial’ and ‘Main Postglacial’ shorelines, provide supplementary information concerning changes of sea-level.