Nantanog

Site of Special Scientific Interest · 53.3244, -4.4364

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Also within

Gwynedd County

Habitats

Fast flowing river and stream

Geology & landscape

Geological Feature: Gorge / Ravine · Geological Period: Ordovician, Precambrian · Rock Type: Conglomerate

Description

Description Nantannog Ravine is of special interest for its geology. The site consists of rock exposures in a ravine and stream section 3.5 km west of Llannerchymedd. The site exhibits important sedimentary features peculiar to the Arenig-Llanvirn Series on Anglesey, and is the type locality for the Nantannog Formation. The exposure features a bedded sequence of shales and sandstones of the Nantannog Formation, with shelly and graptolitic faunas. In the middle of the section, a 20m thick slide conglomerate, derived ultimately from the Precambrian Mona Complex, lies above graptolite-bearing hirundo zone shales. The site contains excellent exposures, illustrative of the sedimentation and stratigraphy of Anglesey in the Lower Ordovician.

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