Mynydd Marchywel is a 418-metre (1,371 ft) high hill in the Neath Port Talbot area in South Wales. Its summit is marked both by a cairn and a trig point. The larger part of the hill is cloaked in modern forestry through which numerous streams fall away westward to the River Tawe, eastward to the River Dulais and southward into the Clydach, the latter two being tributaries of the River Neath.
Geology
The hill is formed from multiple layers of Pennant Sandstone with intervening mudstone layers and occasional coal seams. All are tilted to the south and southwest towards the axis of the South Wales Coalfieldsyncline. Parts of its slopes are mantled by glacial till.[1] The coal seams have been worked extensively in the past. One of the last operations was that at Gleision Colliery under the northwestern side of Mynydd Marchywel.
Scheduled monuments
Mynydd Marchywel summit cairn
This Round cairn dating to the Bronze Age is 10 metres (11 yd) north of the trig pont. The heap of stones, now gradually spreading, has traces of kerbstones amongst the rubble.[2]