Farrant, A R. 2008. A walkers' guide to the geology and landscape of western Mendip. (Keyworth, Nottingham: British Geological Survey.) ISBN 978 085272576 4 The guide is available to purchase from the British Geological Survey https://shop.bgs.ac.uk/Shop/Product/BSP_BWMEND
South flank: Draycott
Cross Swallet, a large closed basin near Westbury-sub-Mendip.
Parking is available at Deer Leap
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]
The Draycott Sleights Reserve offers a glimpse of the underlying geology. At the entrance to the reserve [86]
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]
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]
On the plateau behind Westbury Quarry the road crosses what appears to be a dry valley at Brimble Pit [90]
Three kilometres to the north-west the Somerset Wildlife Trust’s Middledown Reserve [91]
Two other closed basins can be seen: the road from Draycott to Cheddar Head crosses one at Bristol Plain Farm [92]
Two kilometres south-east of Brimble Pit are the Deer Leap and Ramspit nature reserves [94]
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]
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.