South flank: Draycott

Cross Swallet, a large closed basin near Westbury-sub-Mendip.

Parking is available at Deer Leap [ST 519 492] and in many of the villages along the A371.

The southern flank of Mendip between Cheddar and Wells forms an imposing scarp when viewed from the south. Much of the southern facing slope is part of the wildlife rich ‘Mendip Scarp Prime Biodiversity Area’.

The southern margin of the Mendip plateau comprises several stacked ‘sheets’ of Carboniferous Limestone which have been thrust up over each other like a pack of cards along two major thrust faults. These are the ‘South-western Overthrust’ and the ‘Ebbor Thrust Fault’. Although the faults cannot be seen, their presence can be inferred from the juxtaposition of older rocks overlying younger rocks.

Much of the lower slopes between Cheddar and Wells are underlain by a drape of Triassic Dolomitic Conglomerate, which partially buries the Carboniferous Limestone. Known locally as ‘Draycott Marble’, the Dolomitic Conglomerate is composed of cemented fragments of Carboniferous Limestone deposited as scree and slope deposits on the flanks of a rugged mountain range more than 200 million years ago. To the south, away from the Mendips, the coarse conglomerates become finer and grade into the fine-grained Mercia Mudstone.

The hill above Draycott is known as Draycott Sleights [85] [ST 48247 51989]. On Mendip, ‘sleight’ means sheep-pasture, and this site has been managed by traditional sheep-grazing for centuries. Now a nature reserve, Draycott Sleights occupies a steep south-west-facing scarp slope overlooking the Somerset Levels. Its principal habitats are herb-rich limestone grassland with scattered scrub, rocky limestone crags, small cliffs and rock exposures.

The Draycott Sleights Reserve offers a glimpse of the underlying geology. At the entrance to the reserve [86] [ST 48660 51375] outcrops of gently dipping, coarse-grained, red Dolomitic Conglomerate are well exposed in crags in the field to the east of the lane. Rounded fragments of limestone up to 30 cm across are set in a finer matrix of red silt. Some fragments have been dissolved out giving the rock a curious hollow appearance. On the west side of the road, a shallow quarry exposes the Carboniferous Burrington Oolite. Here, the bedding planes are well exposed and close inspection of the limestone will show the small round carbonate ‘ooliths’ from which the rock is composed. The rock here dips to the south at 20°–25°. In the reserve a short distance farther west, the same rock unit can be seen dipping east [87] [ST 48455 51567]. The rocks between the two outcrops have been folded into a small down-fold or syncline. Dolomitic Conglomerate underlies the southern, lower slopes of the reserve, and gives rise to very red soil. The calcareous soil supports a wide range of lime-loving herbs, sedges and grasses. On the slopes the most abundant grasses and sedges include upright brome, crested hair-grass, and glaucous sedge. The grassland is rich in herbs, supporting squinancywort, yellow-rattle, kidney vetch and many other typical species. Orchids that might be seen in summer include pyramidal orchid and greater butterfly orchid.

The northern part of Draycott Sleights supports a slightly different calcareous grassland community, which is dominated by sheep’s-fescue and meadow oat-grass. Many different, low-growing herbs are also present, including the uncommon green-winged orchid in spring. In summer, many different herbs attract butterflies and other invertebrates. Blue butterflies are especially notable, and include the local adonis blue and silver- studded blue. The reserve also has a good snail fauna including the rock-boring dark-lipped banded snail (Cepaea nemoralis) and Helicella itala.

Farther south-east, the hillside above Rodney Stoke is composed mainly of Dolomitic Conglomerate with a few small patches of Carboniferous Limestone poking through. Rodney Stoke National Nature Reserve encompasses broad-leaved woodland, scrub and limestone grassland. Accessible only along the footpath, the woods here are a good example of a typical Mendip ash wood [88] [ST 49111 50867]. Originally managed as coppice the woods are mostly ancient in origin, but were almost entirely clear-felled in the 1914–18 war. Wild service- tree is locally distributed in the wood. Many typical ancient woodland species thrive here, while numerous ferns, bryophytes, fungi, mosses and liverworts flourish in the humid environment.

Farther south-east, there is a lovely view across the Somerset Levels from the top of the hill above Westbury-sub-Mendip. From here, the small Carboniferous Limestone inliers of Nyland Hill and Lodge Hill stand proud of the Somerset Levels. These represent eroded remnants of another thrust sheet of Carboniferous Limestone just appearing through the cover of younger Triassic and Jurassic rocks.

Just below the summit is Westbury Quarry [89] [ST 51560 50000]. Although quarrying has ceased, the site is still operational. In 1969, blasting here exposed a massive sediment-filled cave, at least 70 m long and 30 m high, developed in the Clifton Down Limestone. Within the sediment, well-preserved faunal remains were found, attributed to a Middle Pleistocene interglacial about 620 000 years ago. Between 1976 and 1984 the site was excavated by the Natural History Museum. The upper parts of the deposit yielded abundant small mammal bones and in places remains of the extinct cave bear Ursus deningeri, suggesting that the cave was used as a bear den and an owl roost at different times. The lower part of the sediment fill is thought to be at least 780 000 years old. Much of the deposit is now grassed over.

On the plateau behind Westbury Quarry the road crosses what appears to be a dry valley at Brimble Pit [90] [ST 50850 50800]. In fact, this is a large shallow closed basin formed by dissolution of the limestone. A belt of twelve such basins extends along the southern rim of the Mendip plateau from Cheddar Gorge to Ebbor Gorge. Brimble Pit is one of the largest of the chain. During the last glaciation underground drainage was impeded by permafrost and these depressions became lakes. Their floors are covered with a fine reddish-brown wind-blown silt, or loess, deposited here during the last glaciation. The floor of this particular basin is pockmarked by nine small sinkholes where the loess has subsided into cavities in the underlying limestone. Many of these had been infilled by farmers, but have since been cleaned out by the present landowner.

Three kilometres to the north-west the Somerset Wildlife Trust’s Middledown Reserve [91] [ST 48269 52934] is centered on another of these closed basins. The former lake bed is floored with loess, up to 10 m thick and pockmarked by two very large sinkholes. The loessic silt supports an old hay meadow, while the thin limestone soils around the basin sustain a flower-rich grassland with wild thyme, salad burnet and fairy flax.

Two other closed basins can be seen: the road from Draycott to Cheddar Head crosses one at Bristol Plain Farm [92] [ST 50191 51643], the other, Cross Swallet, can be seen from the Priddy–Westbury footpath [93] [ST 51578 50028].

Two kilometres south-east of Brimble Pit are the Deer Leap and Ramspit nature reserves [94] [ST 51603 49318]. The car park here provides some of the best views across Somerset stretching east from the Cretaceous Upper Greensand scarp on the Wiltshire border across the low Jurassic Polden Hills to the Blackdown Hills, and west across to the Devonian uplands of Exmoor and Quantock. Glastonbury Tor, formed of Middle Jurassic limestone and sandstone, can be seen rising ethereally from the Somerset Levels.

The geology here is quite unusual, being one of the few places on western Mendip where upper Carboniferous rocks are found. The Carboniferous Limestone, which dips to the south at about 25°–30°, is overlain by the upper Carboniferous Quartzitic Sandstone Formation and the Coal Measures (mostly sandstone and shale). A small sliver of wet boggy ground 200 m south-west of the car park marks the outcrop.

However, most of the Coal Measures is cut out by the Ebbor Thrust, which runs through the reserve. Along this fault, the Black Rock Limestone has been thrust over the top of the younger sandstone. Here, the small stream sinks underground into the limestone where it crosses the thrust fault [95] [ST 51508 49106]. The unimproved calcareous and neutral grassland and semi-natural woodland is a rich wildlife habitat. The West Mendip Way runs through the area linking Ebbor Gorge, a short distance to the west, to Cheddar via Priddy and Draycott.

Mendip archaeology

The Mendip Hills are host to many archaeological sites, many of which are underground in caves.The earliest at Westbury-sub-Mendip, was once a cave- bear lair and dates back over 600 000 years. It was later used as an owl roost whose droppings contained small mammal bones. At Banwell, the Bone Cave acted as a pitfall trap into which many ice age animals fell including mammoth, woolly rhino and bison around 75 000 years ago.

Some caves were occupied by humans during the late Upper Palaeolithic  (10 000–8500 BC), including Gough’s Cave in Cheddar, while during the Mesolithic (9000–4000 BC) Aveline’s Hole in Burrington was used as a cemetery. Caves were also used during Neolithic (4000–2000 BC) and Bronze Age (2000–650 BC) times.There are even examples of cave art in Gough’s Cave and Aveline’s Hole.

As well as its caves, other archaeological sites including long barrows, henges, standing stones, round barrows and Iron- Age hill forts can be found.The Priddy Circles are good examples of Neolithic henges, while over 300 Bronze Age round barrows (or tumuli) can be found scattered throughout the region.These were used for burials and were often arranged in linear cemeteries such as Priddy Nine Barrows on North Hill.

Iron Age (650 BC–60 AD) settlements and hill forts occur at Dolebury, Burrington and Maesbury near Shepton Mallet.The Romans left their mark with roads, villas and forts, especially around the former lead mining areas. More recent archaeological sites include a Saxon palace at Cheddar, King John’s Hunting Lodge in Axbridge, the extensive 18th and 19th century mining remains at Shipham, Charterhouse, Priddy and elsewhere, and a Second World War bombing decoy on Blackdown.

Figures

(Figure 86) Draycott Sleights reserve, with dipping Burrington Oolite. © Sharon Pilkington.

(Figure 87) Aerial photograph of the South Flank: Draycott.

(Figure 88) Bluebells in Stoke Wood. © Sharon Pilkington.

(Figure 89) Draycott Marble Quarry. Courtesy J. hanwell Collection.

(Figure 90) Kidney vetch. © English Nature.

(Figure 91) Hyena, which once roamed across Mendip.

(Figure 92) Cave bear tooth from Westbury-sub-Mendip.

(Figure 93) Topographical map of closed depressions.

(Figure 94) Cross Swallet, a large closed basin near Westbury-sub-Mendip.

(Figure 95) Remains at Banwell Bone Cave. © J Chapman.