Rhymney River Section
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Climate exposure
This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.
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
Geology & landscape
Geological Period: Silurian · Rock Type: Sandstone
Landscape processes: Coastal
Description
Description Rhymney River Section is of special interest for its geology. Located along a short tidal stretch of the Rhymney River estuary in Cardiff, it includes 300m of the river and its steep bank. The most accessible and visible rocks are located at river level, and are most completely exposed at low tide. Rhymney River Section contains the most comprehensive sequence of strata in the Cardiff Silurian inlier. These rocks were laid down approximately 420 million years ago, when the area that now forms south Wales lay just to the south of the equator, and was covered by a warm, shallow sea. There are two main rock units, the Cae Castell Formation and the Hill Gardens Formation above, the former laid down during the Wenlock Epoch of the Silurian Period. The river section provides the only opportunity of examining more or less the whole of the local upper Wenlock succession, in particular that part above the Rumney Grit, continuing into the later Ludlow Series, and finally Old Red Sandstone strata. The locality also has some palaeontological significance. Several gastropod and bivalve species from both Wenlock and Ludlow parts of the sequence were first described at this site. Rhymney River Section is used as the ‘type locality’ for these species, and provides a standard against which other fossils from this period found elsewhere in the world are compared.
Plant communities
A9 — Fast flowing river and stream, Marginal and inundation, Pond ditch and canal, Sluggish river and stream
Potamogeton natans community
Show 20 indicator speciesSchoenoplectus 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
Show 15 indicator speciesIsolepis 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
Show 11 indicator speciesBerula 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
Show 12 indicator speciesFontinalis 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