485 Million Years of Accumulated History
The hills are formed largely from the Ordovician age (485 to 444 million years ago) marine mudstones and siltstones of the Penmaen Dewi Shales and Aber Mawr Shale formations which have been intruded by microgabbro (otherwise known as dolerite or diabase) of Ordovician age. The former slate quarries at Rosebush on the southern edge of the hills worked the Aber Mawr Formation rocks whilst it is the dolerite tors of Carn Menyn which have been postulated, amongst other localities, as the source of the Stonehenge ‘bluestones'.
IMG_1281
485 Million Years of Accumulated History
The hills are formed largely from the Ordovician age (485 to 444 million years ago) marine mudstones and siltstones of the Penmaen Dewi Shales and Aber Mawr Shale formations which have been intruded by microgabbro (otherwise known as dolerite or diabase) of Ordovician age. The former slate quarries at Rosebush on the southern edge of the hills worked the Aber Mawr Formation rocks whilst it is the dolerite tors of Carn Menyn which have been postulated, amongst other localities, as the source of the Stonehenge ‘bluestones'.
IMG_1281