Light Clough

Site of Special Scientific Interest · 53.8339, -2.3784

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Also within

Lancashire County

Condition (Natural England)

Favourable (1)
UnitFeatureConditionArea (ha)Assessed
SD751375 — Favourable 0.49 2015-01-14

Habitats

Fast flowing river and stream

Geology & landscape

Geological Period: Carboniferous · Rock Type: Shale

Description

Area,1.08 hectares 2.66 ac Description Light Clough is a small stream on the valley side about two kilometres north east of Whalley which has cut through and revealed the rock strata below. The geological interest of the site, in technical terms, maybe defined as follows, This section has been proposed as the boundary strato type for the base of the Namurian Series and thus also for the base of the Silesian Subsystem. It is the most complete sequence known in the Pennine Trough for this part of the stratigraphical column, showing about 150 metres of shales between the Lyrogoniatites georgiensis Marine Band and the Pendle Grit. Clearly exposed is the Cravenocerasleion Marine Band, which was chosen as the horizon marking the boundary between the Visean and Namurian by the 1935 Heerlen conference on Carboniferous stratigraphy. Since Light Clough is also the type locality for C. leion, the index goniatite for the marine band, it is a site of considerable international importance. 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. Light Clough provides excellent exposures of a series of rock layers originally formed at the onset of the Namurian period of geological history, about 325 million years ago. The rock sequence includes layers of marine shale containing the fossilised remains of sea creatures known as goniatites which are used by geologists to determine the precise age of rocks formed at this time; in fact Light Clough is the type locality for one particular goniatite species. The rock sequence that is exposed includes the base of the Namurian Series and Light Clough is recognised as a particularly valuable locality for geological study. For the reasons outlined above Light Clough has been proposed as the standard for the base of the Namurian Series, which would make it an internationally accepted reference section for this interval of geological time.

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