RECONSTRUCTING QUATERNARY RELATIVE SEA LEVELS FOR NW SCOTLAND USING TRANSGRESSIVE RAVINEMENT SURFACES

Understanding past sea-level changes is important for assessing climate sensitivity and predicting the behavior of ice sheets in response to future warming. Following the Last Glacial Maximum (LGM), sea-levels beneath the former British-Irish Ice Sheet (BIIS) recorded a complex interplay between the retreat of the ice sheet and changing relative sea levels (RSL), leading to a great variety of RSL histories across the British Isles. However, the oldest record of post-LGM sea levels is difficult to determine because the area was either covered by ice and thus a record was not created or is currently flooded by the sea. In this study we examine the sedimentary record of early deglacial RSL changes from cores collected on the shelf of NW Scotland. In particular, we use the formation of transgressive ravinement surfaces (TRS) as an indicator of paleo-sea-level change. The TRS is a stratigraphic surface marking the shoreline migration across the shelf as RSL rose. It is commonly marked by an erosional surface cutting into older glacial-marine deposits and overlain by a transgressive shell lag capped by a transgressive sheet sand. We obtained 4 sediment cores that sampled this surface in present water depths ranging from 123.5–70 m. Radiocarbon ages obtained from above and below the surface place its formation across the NW Scottish shelf from 17.8 To 8.7 ka. Unsurprisingly, the age and elevation suggest considerable spatial variability in the record of RSL change across NW Scotland. These new data provide important new RSL constraints for improving our understanding of glacial-isostatic adjustment, including the timing of ice sheet retreat and the nature of the Solid Earth’s response to that retreat.