Area: 4.77 hectares.
Reasons for notification:
The site is a disused brickpit, which provides the best exposure of Lower and Middle Oxford Clay in southern England, showing a sequence through the jason, coronatum and athleta zones, of Middle Jurassic age.
It is also a nationally important site because it supports an exceptional population of great crested newts Triturus cristatus. The SSSI includes the breeding ponds and the terrestrial habitat that is used by the newts for resting, foraging and hibernation.
Crookhill Brick Pit is located three kilometres to the west of Weymouth. The site is situated on Oxford Clay.
This disused brickpit provides the best exposure of Lower and Middle Oxford Clay in southern England, showing a sequence through the jason, coronatum and athleta zones, of Middle Jurassic age. There are considerable differences in zonal thickness and lithology between this section and the sections in the Midlands, with the grossouvrei subzone being greatly expanded at Crookhill. The clays and shales seen here contain a rich fauna of ammonites, belemnites and bivalves, with the athleta zone fauna being particularly prolific and important. Reineckeid ammonites, usually rare in the British Callovian, occur fairly commonly in the athleta zone here. Crookhill is a key locality for British Callovian biostratigraphy.
Great crested newts
The particular combination and juxtaposition of aquatic and terrestrial habitats provides ideal breeding, foraging and hibernation conditions for the great crested newt. Numbers of newts recorded on the site are exceptionally high for Dorset. The newts depend on water for breeding and particularly favour moderately deep, well-vegetated ponds without fish. The variety of water bodies on the site, which are largely rain-fed and hence of high water quality, provide extremely good conditions for newts. Reeds Phragmites australis dominate the aquatic vegetation of the pond margins and floating vegetation is mainly broad-leaved pondweed Potamogeton natans.
During the first two or three years of life before breeding starts, and outside the spring breeding season, great crested newts are dependent on terrestrial habitats to provide foraging areas and places to hibernate. The terrestrial habitat consists of rough grassland, scrub and the remains of the former brickworks that provide valuable refugia for amphibians.
The open grassland of the southern slopes is a mixture of false oat-grass Arrhenatherum elatius, red fescue Festuca rubra and Yorkshire fog Holcus lanatus, with herbs characteristic of calcareous clay soils such as colt’s-foot Tussilago farfara and bristly ox-tongue Picris echoides. Other herbs scattered in this grassland include yellowwort Blackstonia perfoliata, creeping cinquefoil Potentilla reptans, birds-foot trefoil Lotus corniculatus, common knapweed Centaurium erythraea and grass vetchling Lathyrus nissolia. To the south of the clay pit a small remnant of old grassland has local plants of strawberry clover Trifolium fragiferum and pepper-saxifrage Silaum silaus. The scrub includes bramble Rubus fruticosus, elder Sambucus niger, hawthorn Crataegus monogyna, willow Salix spp. and common gorse Ulex europaeus. The habitats that occur around the ponds on this site are as important as the presence of suitable ponds.
In addition to the reasons for notification, the site also supports populations of smooth newt Triturus vulgaris, palmate newt T. helveticus, grass snake Natrix natrix, slow worm Anguis fragilis, common lizard Lacerta viviparaand adder Vipera berus. Southern hawker Aeshna cyanea and scarce hawker dragonflies Aeshna mixta are also found on the site.
The great crested newt is listed in:
• Annexes II and IVa of the European Communities Directive 92/43/EEC, on the conservation of natural habitats and of wild fauna and flora – the Habitats Directive
• Appendix II of the Bern Convention
• Schedule 5 of the Wildlife and Countryside Act 1981
• UK Biodiversity Action Plan priority species list
This is a Geological Conservation Review (GCR) site.