This is the period during which ice sheets reached their maximum extent in NW Europe. Till of Scottish derivation is found in sediments in the central North Sea dated to around 800 kyr and reflect the former existence of a large ice sheet. The palaeo-temperature graph opposite suggests that ice sheets covered Scotland on many subsequent occasions in the Middle Pleistocene and stratigraphic evidence of many of these ice advances is known from the North Sea and continental shelf west of Scotland.
Glacial deposits extend to the edge of the continental shelf west of Orkney. These deposits include till from the Anglian ice sheet which advanced at around 450 kyr but also younger till sheets. It is likely that Orkney was covered by ice sheets on several occasions.
Orkney is dominated by Devonian sedimentary rocks deposited around 380 million years ago. These rest on basement granites and gneisses around 1000 million years old.
