Devonian Scotland 416-359 million years ago

Between 416 and 359 million years ago, during the Devonian time period, Scotland lay in the sub-tropical region south of the equator, and had a correspondingly hot climate. Rivers eroding the Highland areas carried sediment into lowland areas where it was deposited. Sediment accumulated in lakes and trapped remains of fish and plants between sediment layers. During this time large deposits of sediment were laid down, these are often termed the 'Old Red Sandstone' sediments. The remains of Devonian plants and fish can be found as fossils today, preserved between these ancient sediment layers.

For much of the Devonian, a huge inland lake existed over the areas which are now Orkney and Caithness. At times this 'Orcadian Lake' extended to what is now the south shore of the Moray Firth. Much of the 'Old Red sandstone' makes good building stone and is a distinctive feature of buildings in areas where it occurs locally, such as Strathmore from Blairgowrie and Coupar Angus to Forfar and Edzell.

Devonian rocks now blanket Scotland's older geological foundations in Orkney, Caithness, around the Dornoch and Moray Firths and along the northern edge of the Central belt, south of the Highland Boundary Fault. Smaller areas of Devonian rock occur elsewhere from Shetland to the Southern Uplands.