Onny River Section

Site of Special Scientific Interest · 52.4632, -2.8482

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Also within

Shropshire County Shropshire Hills Scenic Area

Condition (Natural England)

Favourable (1)
UnitFeatureConditionArea (ha)Assessed
SO424853 — Favourable 2.28 2012-01-09

Climate exposure

This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.

Coastal

Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.

Habitats

Fast flowing river and stream

Geology & landscape

Geological Period: Ordovician, Silurian

Landscape processes: Coastal, Fluvial

Description

Description This is a classic geological locality providing important exposures of rocks of the Caradoc Series of the Ordovician System. The rock outcrops are recognised as the standard or type section of the Actonian and Onnian Stages of the Ordovician Period. The site also includes the famous Onny River cliff section showing the discordant contact between these Ordovician rocks and overlying rocks of the Silurian System. This site is of great historical interest, forming part of the area in which the Caradoc Series was originally defined. In addition, the rocks are richly fossiliferous, containing many species of brachiopods, trilobites and, more rarely, graptolites. A number of trilobite and brachiopod species were first defined from material collected here. This is an outstanding and nationally importantsite for geological studies of Ordovician rocks.

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