Beacon Hill

Site of Special Scientific Interest · 52.3818, -3.2039

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Powys County

Habitats

Fast flowing river and stream

Geology & landscape

Geological Period: Silurian · Rock Type: Siltstone

Description

Description Located approximately 4.5 km south of Felindre and 6 km north-west of Llangunllo, the small disused quarries and adjacent stream section on the south-eastern flank of Beacon Hill are of scientific importance because they are the source of most of the specimens of Bohemograptus bohemicus tenuis, the last-known graptoloid species in the British succession. This occurrence enables greater precision in correlating the late Ludlow (Ludfordian) stratigraphy of the Welsh Basin with other contemporaneous rock successions, both nationally and internationally. Exposures of the brachiopod-and bivalve-bearing Knucklas Castle Formation on Beacon Hill comprise alternations of calcareous siltstone and bioturbated siltstone which are of regional importance because they provide a relatively rare opportunity to study the shelf-edge and off-shelf environments that prevailed in this area during the infilling of the eastern margins of the Welsh Basin in late Ludlow times. Remarks: The site is described in the Geological Conservation Review volume entitled ‘British Silurian Stratigraphy’ (Aldridge et al., 2000).

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