Keele Research Repository

Borehole material obtained from the continental shelf and shelf margin around the Shetland Islands has made possible a reconsideration of the glacial history of the archipelago. Analysis of British Geological Survey boreholes, from the areas between 0 and 4°W and 60 to 61°N, and 3 and 4°W and 59 to 60 o N, has revealed an uneven distribution of Quaternary sediments. The Shetland Islands are surrounded by a relatively flat basement platform, beyond which unconsolidated sediments thicken eastwards into the North Sea and westwards across the continental margin. Maximum thicknesses range up to 200 metres, in the vicinity of the modern shelfbreak. Micropalaeontological and sedimentological evidence indicates that these sediments probably date back to the Late Saal. The major part of the sequence relates to the Upper Pleistocene Eemian interglacial, Devensian and Holocene. Environmental reconstructions for these periods indicate that the Shetland Islands were probably ice-free during the Eemian. Subsequently, ice reached its maximum westerly extent during the Early Devensian. The margins of this ice lay to the east and west of the islands, just beyond the margins of the modern basement platform. This indicates a local ice mass debouching from the islands I central watershed. No indigeneous ice appears to have existed during the Late Devensian or the preceding interstadial. During these periods intense periglacial activity occurred. Most of the existing literature describing the glacial history of the Shetland Islands is incompatible with this new evidence. The present study indicates more restricted ice activity in this area than these earlier works suggested, with a much greater emphasis on periglacial activity, particularly during the Late Devensian.