Scottish Highlands in the Torridon Hills such as Liathach and Beinn Eighe in Wester Ross. These foundations are interspersed with many igneous intrusions of a more recent age, the remnants of which have formed mountain massifs such as the Cairngorms and the Cuillin of Skye. A significant exception to the above are the fossil-bearing beds of Old Red Sandstone found principally along the Moray Firth coast and partially down the Highland Boundary Fault. The Jurassic beds found in isolated locations on Skye and Applecross reflect the complex underlying geology. They are the original source of much North Sea oil. The Great Glen
Rùm Torridonian sandstone and shales resting on Lewisian gneiss. Two of the Cuillin are classified as Corbetts: Askival and Ainshval, (Old Norse for "mountain of the ash trees" and "hill of the strongholds" respectively) and Rùm is the smallest Scottish island to have a summit above . Other hills include Hallival, Trollaval ('mountain of the trolls'), Barkeval, and Sgurr nan Gillean (Gaelic: "peak of the young men") in the Cuillin and Ard Nev, Orval, Sròn an t-Saighdeir and Bloodstone Hill in the west. It is likely that only the higher peaks remained above the Pleistocene ice sheets as nunataks. Hallival and