541 – 485 million years ago
During the Cambrian, Scotland lay far south of the equator, and constituted the floor of an ocean called the Iapetus, just off the southern edge of a continent called Laurentia. Northern Scotland lay in the shallowest water where sand and mud was being deposited in fairly shallow waters. This sediment led to the formation of sandstones, limestones and mudstones. These rocks can be found in the far north-west of Scotland, mainly around Assynt, south of Durness and on the Isle of Skye. Fossils of trilobites can be found in these rocks.
Scotland hasn’t always been on the same postion on the face of the Earth and has not always had the same outline. This map shows how ‘Scotland’ may have looked during the Cambrian. Scotland’s present outline has been drawn on the map to help you visualise where the Cambrian rocks that we find today were formed in relation to the surrounding continent and seas.
Elsewhere in Scotland, similar rocks were being formed, however they have experienced a different history since. These more southern rocks were buried deep in the Earth’s crust where they were then deformed and metamorphosed through exposure to high temperatures and pressures, to form rocks such as schist and gneiss. All fossils were destroyed in this process. Since then, through uplift and erosion, they have been brought back up to the surface where they are now the most commonly found rocks across the central Highlands. These rocks are collectively known as the ‘Dalradian’ and the majority of them predate the Cambrian, being as old as 750 million years.
* This map is a schematic reconstruction of what Scotland MAY have looked like at a particular point during the Cambrian – it is only a representation of Scotland’s ancient palaegeography, not the most accurate scientific palaeogeographic reconstruction. (c) Image reproduced by kind permission of The trustees National Museums Scotland