As no sediments of this age are known on land in Scotland, the main events can only be inferred by reference to offshore sediments. The temperature curves derived from careful analysis of oxygen isotopes in North Atlantic sediments indicate that the Early Pleistocene between 0.74 and 2.4 Ma was a period of multiple warm and cold cycles with a periodicity of around 40 ka. The intensity of these cycles did not match, however, those of the Middle and Late Pleistocene. It is generally supposed therefore that the Early Pleistocene was a period of restricted glaciation in Scotland, with alpine glaciers forming in the mountains during cold phases. It is possible that Enegar’s corrie was initiated at this time.
This picture is almost certainly over-simplified. The first arrival of ice-rafted debris in North Atlantic sediments occurs as early as 2.4 Myr. The first evidence of Scottish ice sheets in the northern North Sea is at around 1.1 Myr. The Scottish Highlands, including the Cairngorms may therefore have supported ice caps and even small ice sheets at intervals during the Early Pleistocene.
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.
