Foel Gron Stream Sections

Site of Special Scientific Interest · 52.8390, -3.8019

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Also within

Gwynedd County Eryri / Snowdonia National Park

Habitats

Fast flowing river and stream

Geology & landscape

Geological Period: Cambrian

Description

Description Foel gron Stream Sections is of special scientific interest for its important fossil-based bearing exposures of latest Cambrian age which have facilitated correlation with strata of a similar age found elsewhere in Britain and Scandinavia. The site incorporates two stream sections located on the northern flank of the Rhobell Fawr massif, between the hills of Rhobell-y-big and Foel Gron, approximately 10km south-east of Trawsfynydd. This classic site contains exposures of the upper part of the Dolgellau Member (Merioneth Series, Upper Cambrian) of the lower Cwmhesgen Formation. Fossil assemblages indicative of the lower subzones of the Peltura scarabaeoides Zone are found and include many species of trilobite (especially Ctenopyge of correlative values) and other taxa. The assemblages are the richest for this age known in Wales. The faunas enable correlations to be made with strata in the western Harlech Dome, the Malverns, Nuneaton and Scandinavia. The site's proximity to the internationally important Bryn-llin-fawr site, and the complementary information it provides on this section, emphasize its stratigraphical importance.

Plant communities

A9 — Fast flowing river and stream, Marginal and inundation, Pond ditch and canal, Sluggish river and stream

Potamogeton natans community

Schoenoplectus lacustris, Juncus bulbosus, Sparganium angustifolium, Sparganium erectum, Sparganium minimum, Alisma plantago-aquatica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Elodea canadensis, Lemna minor, Lemna trisulca, Nymphaea alba, Callitriche platycarpa, Callitriche stagnalis, Littorella uniflora, Potamogeton natans, Ranunculus trichophyllus, Glyceria fluitans, Chara subspinosa

A14 — Fast flowing river and stream

Myriophyllum alterniflorum community

Isolepis fluitans, Juncus bulbosus, Fontinalis antipyretica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Lemna minor, Callitriche stagnalis, Littorella uniflora, Potamogeton filiformis, Potamogeton gramineus, Potamogeton natans, Ranunculus peltatus, Chara spp., Nitella hyalina

A17 — Chalk river and stream, Fast flowing river and stream

Ranunculus penicillatus ssp. pseudofluitans community

Berula erecta, Nasturtium officinale, Elodea canadensis, Lemna minor, Callitriche stagnalis, Veronica beccabunga, Polygonum amphibium, Polygonum hydropiper, Potamogeton crispus, Potamogeton pectinatus, Ranunculus penicillatus ssp. pseudofluitans

A18 — Fast flowing river and stream

Ranunculus fluitans community

Fontinalis antipyretica, Fontinalis squamosa var. curnowii, Myriophyllum alterniflorum, Myriophyllum spicatum, Elodea canadensis, Mentha aquatica, Lemna gibba, Lemna minor, Potamogeton perfoliatus, Ranunculus fluitans, Glyceria fluitans, Phalaris arundinacea