Nant y Graen a Nant Ganol
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Geology & landscape
Geological Period: Cambrian, Ordovician
Description
Description Nant y Graean a Nant Ganol is of special scientific interest because it displays sections through the Upper Cambrian Maentwrog Formation from which the biostratigraphy of the three subzones of the Olenus Biozone can be inferred more readily than anywhere else around the Harlech Dome. The site is also of national importance because it enables correlation with other stratigraphical sequences both in Britain and elsewhere in Europe. The site is located approximately 5km south-east of Trawsfynydd and incorporates four separate localities situated on, or close to, minor tributaries of the Afon Gain. Nant y Graean a Nant Ganol is located on the crop of the Maentwrog Formation (Merioneth Series, Upper Cambrian) of the Mawddach Group and demonstrates to advantage the development and sequence of the Olenus Biozone faunas in North Wales. Fossil assemblages indicative of the gibbosus, truncatus and cataractes regional subzones are present and facilitate correlation with strata in the English Midlands, Poland and the standard Scandinavian zonal succession. This is a nationally important site, in the classic ground of North Wales, which illustrates the relationship between lithostratigraphy and biostratigraphy in these Upper Cambrian rocks. Remarks: This site has been selected as a result of the former Nature Conservancy Council’s Geological Conservation Review, a national survey and evaluation of sites of geological and physiographical interest. The site is described in the GCR volume entitled British Cambrian to Ordovician stratigraphy (Rushton et al. 1999). The site lies within Snowdonia National Park.