Hillcollins Pit

Site of Special Scientific Interest · 51.9203, 0.0953

Also within

Hertfordshire County

Condition (Natural England)

Favourable (1)
UnitFeatureConditionArea (ha)Assessed
TL441267 Favourable 0.23 2022-01-20

Description

Area, 0.2 ha. 0.5 ac. Description This site is a small gravel pit exposing the Westland Green Gravel, the earliest irrefutable stage of the Thames; the extent of the gravel coinciding with the former course of the river from the Goring Gap to Norwich. The original type site at Westland Green has become completely degraded and the present site should be considered as the new type site of the Westland Green Gravel. Because of its considerable antiquity and degree of dissection, exposures in this material are infrequent, but since it representsthe earliest course of the River Thames recognised to date the deposit is of considerable significance and the Hillcollins Pit is of major importance in reconstructing the evolving geography of South eastern Britain. Other Information This is a new site identified as being of national importance in the Geological Conservation Review.

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