Date and Time
Velvet Bottom, Priddy, Mendip, Somerset, BS40 7XR
Field Trip Description
At Charterhouse we shall observe the relationship between the land-forms and the geology, especially the three main rock types, i.e. Devonian clastic sediments, Lower Carboniferous shales and limestones. The additional feature which is well seen here is the site of extraction of lead ore over the past two millennia, dating back at least to the Roman occupation of Britain, and the more recent evidence for local smelting of lead from the mineral veins.
At Burrington we shall examine in greater detail the lithologies and fossil content of the above-mentioned sediments, especially those of the limestones, but also a little of the shales. Loose specimens of the Devonian sandstone are also present in the lowest parts of the combe, and in addition we shall see sedimentary deposits from the Palaeozoic/Mesozoic transition of the Triassic sequence, represented here by coarse conglomerates which rest on an early valley floor formed when the combe was a desert wadi on the slopes of the newly elevated hills.
Suggested maps and reading - The best local topographic map would possibly be the O.S. 1:25,000 Explorer series ‘Mendip Hills West’, although there is now the very useful B.G.S. guide ‘Western Mendip’ which includes a really clear geological map at the same scale with more detailed inserts for Burrington and elsewhere, and could easily be used for grid. refs. This would make a very useful purchase as it includes a detailed explanatory booklet about the geology and local history. In order to better appreciate the detailed lithologies a hand-lens would be of great use.
Car parking - The public car-parking area/s at Charterhouse include an off-road area with parking for six to eight normal sized vehicles at ST 505 556 and on the public roadside room for around a dozen vehicles at ST 503 555. If both of these are full there is car-parking in off-road space for several vehicles at St. Hugh’s church at ST 502 557. Suggested driving time from Bath centre around 1 hour.
Field trip assembly point is at the roadside at the stile into Ubley Warren, ST 504 554 at 10.30 a.m. The walking distance in the morning will be around one mile at a gentle pace over reasonably level ground, mostly on paths, with minor climbs of about 20-30 metres, some rocky ground, but mainly smooth grassy areas and gravel. There are no public facilities at all at Charterhouse, although there is a field study centre nearby (ST 503 557).
The morning will conclude at lunch-time, around 1.00 p.m. and the next venue is at Burrington Combe, to which cars could drive for lunch and toilets, both public and private (in the café) are available. The afternoon session will start from the roadside at the public toilets ST 477 587 and will begin at 2.00 pm unless adverse weather alters plans. There is usually adequate parking somewhere in the lower stretch of the combe, but if not nearby it may be necessary to walk up from a large area around 200 metres to the north on the roadside, formerly used by the now defunct garden centre. Otherwise there is quite a lot of roadside parking a little further up the combe, again a few hundred metres away. The afternoon session will involve some half mile of roadside walking, and optional extra few hundred metres off-road along (through!) a shallow stream, where waterproof boots would be advantageous. There is a moderate climb throughout the outward leg of this walk, maybe 100 metres in all.
The walks will offer little shelter, especially if windy, so bring warm and waterproof clothing and stout footwear is essential. Wellington boots are a suitable alternative for the afternoon session, but strong gripping soles better in the morning, when the ground should be fairly dry, but the grass is often slippery. Hard hats are always a good idea, although there is no need to expose oneself to immediate hazards from falling rock. Hammering of rocks is to be avoided, these are protected sites and loose material is plentiful.
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