Palaeoenvironmental significance of marine and terrestrial Tertiary sediments on the NW Scottish shelf in BGS borehole 77/7

BGS borehole 77/7, located to the north of Scotland, drilled through Quaternary deposits into Neogene and Palaeogene sediments before terminating in Lewisian basement. The pre-Quaternary rocks have been analysed using a variety of petrological, geochemical and bio-stratigraphical techniques. The basement comprises amphibolite schist, and has a deeply weathered surface which, it is argued, is likely to have developed during the early Eocene. Overlying terrestrial lignitic deposits are palynologically dated as upper Oligocene; they were deposited in a forest swamp environment at a time of hinterland uplift, and are comparable with sediments of similar age and character found in basins along the length of western Britain. Following a rise in sea level, marine conditions prevailed during the Miocene, as recorded by glauconitic siltstones which are of a facies that is extensively developed on the outer shelf and slope NW of Scotland.