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Mynydd Machen is a hill lying between the town of Risca and the village of Machen in Caerphilly county borough in South Wales. Its summit is crowned by a trig point and a mast. == Geology == The hill lies at the southeastern extremity of the South Wales Coalfield where the varied Carboniferous Period rock strata of the coalfield margin are tilted steeply northwestwards into the coalfield basin. The sequence which outcrops on Mynydd Machen in northeast-southwest aligned bands is this (oldest at base): Warwickshire Group : *Pennant Sandstone Formation :: *Brithdir Member :: *Rhondda member :: *Deri Member South Wales Coal Measures Group : *South Wales Middle Coal Measures Formation : *South Wales Lower Coal Measures Formation Marros Group : *Bishopston Mudstone Formation : *Twrch Sandstone Formation Pembroke Limestone Group The summit of the hill is formed from the sandstone of the ‘Brithdir Member’ of the Pennant Sandstone Formation. A large quarry towards the south of the hill works the dolomitic limestone of the Pembroke Limestone Group.〔British Geological Survey 1:50,000 map sheet 249 ''Newport'' & accompanying memoir〕〔(BGS ‘Geology of Britain’ viewer )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mynydd Machen」の詳細全文を読む スポンサード リンク
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