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Nod Glas Formation

Ordovician System of EuropeRock formations of WalesUpper Ordovician Series
River bed of Afon Ddu
River bed of Afon Ddu

The Nod Glas Formation (also known as the Nod Glas Black Shale, the Cadnant Shale, the Penarwel Mudstones or just Nod Glas) is an Ordovician lithostratigraphic group (a sequence of rock strata) in Mid Wales. The rock of the formation is made up of pyritous, graptolitic mudstone that is generally black in colour. It weathers to a soft, very well cleaved and coal-like material. The formation runs from Conwy in the north, down to Cardigan Bay in the area around Aberdyfi and Tywyn, though it is not a continuous over this area.The formation is the topmost of the Caradoc Series in North Wales, and the name refers to all the black shale beds in the area. In South Wales, the equivalent beds of shale are called the Dicranograptus Shales.

Excerpt from the Wikipedia article Nod Glas Formation (License: CC BY-SA 3.0, Authors, Images).

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Latitude Longitude
N 53.177 ° E -3.8407 °
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LL32 8JX , Dolgarrog
Wales, United Kingdom
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River bed of Afon Ddu
River bed of Afon Ddu
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