(4540 – 542 million years ago)
No rocks of this age are known to be exposed at the surface within Fforest Fawr Geopark though they will certainly exist at great depth.
The nearest exposures of rocks of this age are to be found in Pembrokeshire to the west and in the area of the Malvern Hills to the east. Wales’ oldest rocks – all Precambrian – are found on Anglesey and near the English border at Kington.
What’s in a name?
The term ‘Precambrian’ was originally used to refer to any rocks older than the Cambrian Period. Unlike the Cambrian, Silurian etc it is neither a ‘period’ nor an ‘era’ in the strict sense of these terms. The Precambrian accounts for 90% of the age of the Earth and is nowadays subdivided into many ‘eons’.