Pre-Cambrian

The Precambrian rocks in Pembrokeshire are found in two complex bands that run eastwards from the north and south sides of St Bride’s Bay.

Volcanic rocks are exposed as dramatic outcrops and also in cliff sections, along the coasts, in the St. David’s area. Tuffs, formed of soot and marine muds, and rhyolite, a volcanic lava, are the two common rock types found. Granites and diorites intrude extensively in the southern band running from Talbenny to Benton.

Precambrian rocks are associated with poor acid soils in the treeless coastal area of North Pembrokeshire. Here the soil is thin and the environment only allows for the survival of certain types of plant. Purple Moor Grass and heathers predominate in this bleak exposed landscape.

Igneous rocks are hard and strong. For this reason they were sought out by people in the Neolithic period and made into fine polished stone axes. Axes made from Precambrian igneous rocks have been found in the area. They were used by these early farmers to clear the land for agricultural use.