Robin Hood's Bay: Maw Wyke to Beast Cliff

Also within

North Yorkshire County NORTH YORK MOORS National Park Cleveland Way National TrailCoast to Coast National TrailKing Charles Way - Filey Brigg to Newport Bridge National Trail

Condition (Natural England)

Climate exposure

This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.

Habitats

Bracken scrub, Mixed scrub, Montane scrub

Geology & landscape

Geological Feature: Rock Outcrop · Geological Period: Jurassic · Rock Type: Ironstone, Mudstone, Sandstone, Shale, Siltstone

Landscape processes: Coastal, Glacial, Periglacial

Description

Description This site consists of part of the North Yorkshire coast in the vicinity of Robin Hood's Bay, north of Scarborough, from Maw Wyke and Hawsker Bottoms at the northern end to Beast Cliff at the southern end. The site is of importance for five distinct areas of geological interest, the coastal/woodland vegetation at Beast Cliff and the zonation of marine biotopes on the rocky foreshore. Geology The coastal cliffs and foreshore exposures around Robin Hood's Bay and Ravenscar constitute one of Britain's classic geological localities and have been studied from at least the 1820s. The site includes an unrivalled and continuously exposed Lower Jurassic sequence dominated by mudrocks of the Lias Group and capped by sandstones of the Ravenscar Group of early Middle Jurassic age. Throughout the succession there is excellent bio and chronostratigraphic control based on a very detailed sequence of ammonite faunas. Many of these faunas form the basis for the formal definitions of Biohorizons, Subzone and Zones and the site is therefore of very great importance to European Jurassic chronostratigraphy. The area has also yielded the type specimens of the index species of many of these units. The Lias Group, represented in ascending order by the Redcar Mudstone, Staithes, Cleveland Ironstone and Whitby Mudstone Formations contains stratotypes for several zones and horizons. This includes a very complete Sinemurian Pliensbachian boundary sequence within the Redcar Mudstone Formation, which may become a Global Stratotype Section and Point. Other highlights include a well preserved succession of biostratigraphical horizons within the Cleveland Ironstone and the most complete Toarcian succession in Britain represented by the Whitby Mudstone Formation. This Lower Jurassic succession is also of great interest for its sedimentology and its fossil invertebrate faunas which both provide insights into the environmental conditions of the time. Occasional marine reptiles ichthyosaurs and crocodiles have been recovered from various levels. The base of the Middle Jurassic sequence is well exposed around Blea Wyke and includes a relatively thick Dogger Formation with a famous and fossiliferous 'Nerinea Bed' of Aalenian Opalinum to Murchisonae Zone age. The succeeding dominantly, non marine Ravenscar Group is well developed including its component Saltwick, Eller Beck, Cloughton and Scarborough Formations Aalenian to Lower Bajocian. In the Beast Cliff area a number of plant bearing horizons occur within the Saltwick and Cloughton Formations. Many species occur which are seldom found at Yorkshire's other famous Jurassic plant localities. Many species of filicales, bennettitales, cycads and conifers are recorded from Beast Cliff; a prolific palaeobotanical locality with notable rarities. Maritime The shores of Robin Hood's Bay between May Wyke and Beast Cliff are predominantly rocky and moderately exposed to wave action. The varied geology along this coast plays a major role in creating an exceptionally wide range of habitats and associated communities for this part of the North Sea coast. Extensive examples of two rocky shore habitats are found here, moderately exposed flat bedrock and moderately exposed large and massive boulder fields. Slightly more exposed areas of the shore, such as at Whitehouse Hole are characterised by biotypes more typical of wave exposed shores. Areas of gently dipping mudstones, shales and ironstones at the northern end of the site are characterised by complete zonation of rocky shore biotopes from the lichen dominated Verrucaria maura biotope at the top of the shores, through fucoid biotopes characteristic of moderately exposed shores Pelvetia canaliculata, Fucus spiralis, Fucus vesiculosus, F. serratusinto the kelp zone Laminaria digitata the latter which straddles the low water mark. In the Far Jetticks area, good quality, extensive areas of two nationally scarce red algal turf biotopes Osmundea pinnatifida and Corallina officinalis replace the more common fucoid dominated biotopes and occupy much of the intertidal zone from the base of the cliff to the kelp zone. Here, the finely roughened bedding planes of mudstones belonging to the Cleveland Ironstone Formation provide surfaces for the firm attachment of holdfasts. The low shore kelp zone Laminaria digitata straddles the low water mark and forms the transition to highly rated subtidal kelp forest biotopes. Robin Hood's Bay contrasts well with the Maw Wyke area as it is slightly more sheltered but still falls within the moderately exposed selection unit. This area is particularly noteworthy for its rich and varied low shore communities, particularly the Fucus serratus and Laminaria digitata biotopes on bedrock and boulders. The presence of the relatively stable medium and large boulders provides additional habitats beneath and between the boulders for a wide variety of animal groups including sponges, anemones, bryozoans, crabs and shore fishes. Along the southern section of the site, the shore between Blea Wyke and Beast Cliff is predominantly composed of large and massive boulders resting on a mudstone platform. The biology of this area again demonstrates the underlying effects of active geological processes. The upper shore lacks typical fucoids and is instead made up of ephemeral communities of green and red algae Enteromorpha sp. and Porphyra sp. This composition reflects the unstable nature of the friable upper shore talus beneath the cliffs. In the mid and low shore areas the boulders are characterised by typical biotopes of fucoids, kelps and red algal turfs. Areas of the shore lying below recent stumps, are dominated by dense turfs of the nationally uncommon sand binder red algae Rhodothamniella floridula biotope which tolerates sediment scouring by binding sediment to form a cushion like turf. Hawsker Bottoms is also a key palaeobotanical and stratigraphical site and has the best inland exposure of the Scarborough Formation, here near the northern limit of its outcrop. It has provided one of the most varied fossil faunas from this portion of the Middle Jurassic, including the only corals so far recorded from this formation. The nearby Maw Wyke is an outstanding locality of national importance for the study of fossil ferns. A lens, within the Saltwick Formation, yielded particularly fine examples of the genera Coniopteris, Cladophlebis and Phlebopteris including fertile axes essential to systematic studies. Robin Hood's Bay is an important site for coastal geomorphology for a series of well developed shore platforms cut mainly across the outcrops of Lower Lias shales siltstone rhythms. The surface morphology of the platforms reflects the arrangement of bedding withina broadly anticlinal structure which has been planed off. The cliffs near North Check and South Check include Middle Lias sandstones, relatively more resistant than the Lower Lias shales, whilst those within the Bay predominantly occur in Lias shale till and are locally affected by considerable mass movements. Robin Hood's Bay provides important contrasts with other platform sites, firstly through its location within the area affected by North Sea wave climates and secondly in having been subject to glacial and post glacial processes prior to sea level reaching its present condition. The greater variety of interest, stratigraphical, palaeontological and geomorphological, make the Hawsker Robin Hood's Bay Ravenscar Beast Cliff area one of the most famous and important for British Geology. Biology Much of Beast Cliff is covered by scrub and woodland. Ash Fraxinus excelsior dominates the canopy with birch Betula spp., hazel Corylus avellana and field maple Acer campestre, although in more acidic situations oak Quercus aff. robur, rowan Sorbus aucuparia and holly Ilex aquifolium are frequent. great wood rush Luzula sylvatica is abundant on the steep flushed slopes, whilst dog's mercury Mercurialis perennis and opposite leaved golden saxifrage Chrysosplenium oppositifolium are plentiful in the ground flora of the terrace. Sandstone boulders support a luxuriant growth of mosses and ferns, including hart's tongue Asplenium scolopendrium and soft shield fern Polystichum setiferum. Pools on the cliff shelf have been colonised by common club rush Schoenoplectus lacustris and are fringed by alder Alnus glutinosa, willow Salix spp. and greater tussock sedge Carex paniculata. North of Beast Cliff the vegetation is more open and reflects alternating strata of rich and poor base status. Typical of more calcareous clays are quaking grass Briza media, glaucous sedge Carex flacca, kidney vetch Anthyllis vulneraria and grass of Parnassus Parnassia palustris, whereas heather Calluna vulgaris, bell heather Erica cinerea, crowberry Empetrum nigrum, golden rod Solidago virgaurea and wavy hair grass Deschampsia flexuosa characterise more acidic sandstone outcrops. Bracken Pteridium aquilinum and various shrub species such as gorse Ulex europaeus, broom Cytisus scoparius, goat willow Salix caprea and rowan Sorbus aucuparia are present in varying densities over much of the site.

Species mentioned

Plant communities