Allt Penycoed Stream Section

Site of Special Scientific Interest · 51.8400, -4.2606

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Also within

Dyfed County

Habitats

Fast flowing river and stream

Geology & landscape

Rock Type: Shale

Description

Description The most complete section in the Cwmffrwd Member of the Arenig Carmarthen Formation. This is the best exposure through the thick turbidite/shale sequence which makes up this unit, showing the base of the member and good sections in the underlying Pibwr mudstones. The latter shows changing trilobite faunas indicative of significant ecological changes related to water depth and oxygenation. An important site with ecologically and stratigraphically significant trilobite faunas and sediments. In layman's terms, the interest of this site may be expressed more simply, and such a statement is provided below. This should not be taken as definitive and further information as to details of the interest can be obtained from the Nature Conservancy Council.This stream section provides important exposure of a sequence of fossil-bearing sandstones and muds which were deposited in deep-water marine conditions some 500 million years ago. The fossilised remains of a new extinct group of sea-living arthropods, known as trilobites, have been recorded from this area and have helped geologists understand the conditions which existed on the sea bed during the period when sediment was accumulating. The rich fossil assemblage described from Allt Penycoed has also allowed geologists to compare this section with rocks of a similar age throughout South Wales and the rest of the British Isles.

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