The Brecon Beacons: Pen-y-Fan and Corn Du Alex Gibson
PEN-Y-FA N and Corn Du in South Wales' Brecon Beacons are the highest points in southern Britain. At around 2900ft, they command spectacular views to Cader Idris, in the Snowdonia National Park, 70km to the northwest, and to the Severn Estuary and the north Devon hills to the south. These views and the dramatic cliffs of the northern escarpment attract over 50,000 visitors a year. In addition, large numbers of the armed forces train here throughout the year.
The pressure caused by so many visitors is having a devastating effect on the sandstone upland, and erosion is a very serious problem. The vegetation and topsoil have disappeared from large areas of the summits and their approaches, and Bronze Age cairns on Pen-y-Fan and Corn Du were disappearing at an alarming rate. Stones from the cairns were being dislodged and removed, many for weather shelters and still others were being thrown over the cliff edge.
The National Trust, landowners of the area, were concerned about the damage being caused to the archaeology, so they commissioned the Clwyd-Powys Archaeological Trust to survey both cairns in May 1990. A subsequent visit to Pen-y-Fan in October 1990 demonstrated the rate of this destruction; half the cairn had completely disappeared.
Rescue excavations were mounted in 1991 (Pen-y-Fan) and 1992 (Corn Du) to recover what archaeological deposits remained before both cairns were completely destroyed. Due to the positions of the cairns, both excavations were logistically difficult but, thanks to 666 Squadron, Army Air Corps, we were able to have our site-hut and equipment airlifted at the start and end of each season ... we had to climb up every day between times!
Both cairns were built in similar ways. Firstly, a massive central cist was constructed on the turf of the old ground surface. Presumably each originally contained a burial, but if so, they had long been robbed: we found nothing in them. A turf and peat mound was then piled around this. Finally a capping of large sandstone slabs was pitched over the top of the turf mound.
This led to the most spectacular results of the excavation, for the stone capping compressed the turves and created anaerobic conditions which preserved both the turves of the mounds and the grass of the old ground surface. Indeed, such was the preservation that many plants had retained their original colour - though they oxidised quickly on being exposed to the air.
Individual plants could be recognised bilberries, heather, mosses and cotton grass retaining their greeny-brown colours. Insect remains were abundant within the grass and some petals have also been tentatively identified which may provide information about the exact time of the year that both sites were constructed.
Preliminary pollen analysis indicates that cereals were being grown in the vicinity and that the tops were being grazed. Hazel stakes were found, with axe marks from narrow-blade axes. They were probably debris discarded by the cairn builders, for none were stuck in the ground, but all lay casually on the old ground surface where they had been dropped. Clearly a great deal of environmental work lies ahead for the palynologists and palaeobotanists.
Already a radiocarbon date of 1640 ± 90 bc has been obtained from the turf line of the old ground surface beneath Pen-y-Fan, and dates of 1850 and 1745 (both + 75) bc have been obtained from Corn Du. A calibrated date before 1900 BC seems not unlikely.
The two cairns differed in details. At Pen-y-Fan a small bronze hoard comprising a ring fragment and part of a basal-looped spearhead were recovered from a disturbed part of the cairn. The finds date to the Late Bronze Age, a thousand years after the cairn had been constructed.
Corn Du differed slightly in that the central cist was surrounded by a polygonal
Two Bronze Age cairns have been excavated on the summits of the Brecon Beacons. Here we see the burial cist found at the centre of the cairn at Pen-y-Fan. Unfortunately it had been robbed.
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