Cambrian

The Cambrian period began 570 million years ago and ended 500 million years ago. During this period, what was to become the British Isles was submerged under sea and located near the Equator.

Cambrian rocks occur mainly in north Pembrokeshire and are sedimentary rocks formed from solidified material on the Cambrian sea bed.

Sedimentary rocks from this period can be seen in cliffs at bays around St. David’s peninsula, such as Whitesand’s, St. Non’s, Carfai and Caerbwdi. A variety of rock types occurs such as red conglomerate, green sandstone, red shale, pebbly sandstones and mudstones. Some of the earliest marine fossils, known in Pembrokeshire, are found in the red shales around Caerfai. Trilobites, brachiopods and crustaceans found.

Cambrian rocks have weathered over millions of years in the area to produce thin, stony sandy soils. In sheltered valleys, woodlands and marshy hollows are frequent, while exposed hilltops dry heathland vegetation is found. In the cliffs the rocks erode leaving ledges, ideal nesting sites for thousands of sea birds.

The soils of the area are also excellent for cultivation and in the last century oats and barley were grown here. The Cambrian sedimentary rocks are excellent for building purposes. Caerbwdi sandstone, with its distinctive purple and green colour was used to build St. David’s Cathedral.