Wales (Cymru) - Southeast Wales

This area encompasses the rural mainly upland area located southeast of the Welsh Borderland Fault, bounded on its southern margin by the edge of the South Wales Coalfield with the eastern boundary located along the Welsh Border. Much of this area comprises a series of steep escarpments such as Mynydd Epynt and the Brecon Beacons, with intervening slopes forming rolling farm land. There are few large settlements, the main towns include Brecon and Abergavenny.

Sedimentary Bedrock

The only sedimentary bedrock in this area is referred to by geologists as the Old Red Sandstone, which was deposited in deserts and rivers between 420 and 360 million years ago. This comprises a sequence that is several kilometres thick of reddish sedimentary rocks that dip gently toward the south and southeast and can be seen in the escarpments of the Brecon Beacon mountains (Figure 7).

Basement rocks

In the west of the area, units of mudstone, sandstone and limestone deposited between around 430 and 420 million years ago are exposed. These are thought to pass at depth beneath the Old Red Sandstone. Although these rocks do not currently constitute a major aquifer in Wales, the abstraction of groundwater for private supply is widespread.