The Holocene palaeoceanographic history of Muck Deep, Hebridean shelf, Scotland: has there been a change of wave climate in the past 12 000 years?

Abstract. Depressions (known as deeps) on the Scottish continental shelf are sediment sinks and they, thus, provide important sources of information on past oceanography and climate. Muck Deep is a partially infilled relict glacial valley cut in the continental shelf. A 70 cm core shows an upper buff sandy mud layer (0–4500 BP, radiocarbon years) overlying a dark grey mud layer (4500–12 000 BP). The foraminiferal faunas suggest that the upper sandy layer formed under higher energy conditions comparable to those existing now, where storm waves from southwesterly gales are responsible for transporting material from the adjacent shelf into the deeps. The grey mud formed under lower energy conditions as a consequence of lower storm wave influence on the sea floor (therefore, reduced transport of tests from the shelf into the deep). Because of the interaction of changing sea-levels and glacial rebound, water depths over Muck Deep were 35 m greater at 14–15 ka and have never been less than now. Therefore, the likely explanation of the lower energy deposits at the base of the core is related to the impact of storm waves on sediment transport from the adjacent shelves. Either water depths over the adjacent shelves were too great to be influenced by storm waves or the wave climate (direction) differed at that time.