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| A view up Lathkill Dale |
Following on from a visit to a few sites in Doncaster in March 2022, the next Sheffield U3A Geology Group field trip took place on a fine April day, to investigate the Carboniferous Limestone of Upper Lathkill Dale in the Peak District National Park.
Setting off from the meeting place next to the public toilets, to the east of Monyash, we headed east along Church Street until we found the footpath that leads down to Ricklow Dale, a now dry shallow tributary of Lathkill Dale where the Eyam Limestone is exposed.
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| The Eyam Limestone Formation in Ricklow Dale |
At the end of the dale, we then went to investigate the Ricklow Quarry, a SSSI (Site of Special Scientific Interest) that exposes a section through an outstanding example of a shelf developed reef, composed of carbonate mud mounds, which was fringed with crinoids and contains some of the UK’s best specimens of Gigantoproductus brachiopod fossils.
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| Ricklow Quarry |
We didn’t get to see any beds with brachiopods, but there were many good examples of crinoid stems, which had weathered proud of the calcite matrix. The crinoidal limestones in the Monsal Dale Limestone were once widely quarried and polished, to produce decorative stone for fireplaces and floors, but the only remaining source is the Once-a-Week-Quarry at nearby Sheldon.
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| Crinoid stems |
The quarry is on the edge of Lathkill Dale and although most waste rock was tipped into the valley bottom, there was plenty of stone lying around the quarry floor. Although it is illegal to collect samples from the rock face at SSSIs, I was able to obtain specimens of a brachiopod and crinoidal limestone from these using my Estwing hammer.
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| Specimens with brachiopods and crinoids |
After taking lunch, we then followed a path along the edge of the dale, where there were excellent views of its morphology and the various horizontal beds of Eyam Limestone exposed in the upper section, with the lower Monsal Dale Limestone covered by a thick scree slope.
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| A view down Lathkill Dale from Ricklow Quarry |
Making our way slowly down a steep and sometimes precipitous path, we eventually reached the bottom of the dale before having a quick look at the scree formed by waste rock from Ricklow Quarry. We didn't see any obvious reefs that apparently appear in the upper parts of the exposed limestone and headed east down the dale.
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| Views at the bottom of the path descending into Lathkill Dale |
No rock exposures could be explored at low level due to the covering of scree, so we continued along the path for a few hundred metres before stopping at Lathkill Head Cave, from which the River Lathkill emerges when there are high levels of rainfall and groundwater, but which ceases when the water table drops.
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| Lathkill Head Cave |
When exploring the rock strewn temporary stream bed that leaves the cave, I found a large piece of limestone that contains several brachiopods with well preserved fine ribs and some crinoid stems - possibly from the Lathkill Shell Bed, which forms a distinctive marker horizon. Being persuaded by one of the group members not to beak off a piece, when I cleaned it of dirt and algae at home, the fossil casts are revealed to be brown in colour, with the binding matrix being white.
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| A large specimen with brachiopods and crinoids |
Lathkill Dale is a dendritic dry valley system, which is deeply entrenched into a karst plateau, and opposite Lathkill Head Cave, another former water course or waterfall has cut a nick into the Eyam Limestone to form quite a distinctive feature.
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| A tributary valley |
Continuing down the dale, deposits of calcite on the rocks mark the intermittent course of the river and, after a short distance, water was flowing from another spring that feeds the River Lathkill but before we reached Pudding Springs, which flows permanently except in times of severe drought, we crossed the footbridge and headed up Cales Dale.
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| A spring feeding the River Lathkill |
Walking along the path, we stopped to look at a block of limestone embedded in it, which contains a good example of corals – probably of the genus Lithostrotion or Diphyphyllum, which we had seen before in the Monsal Dale Formation at Hob’s House and Eyam.
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| A block of limestone with corals |
Leaving Cales Dale by a steep path that led up to the limestone plateau, we encountered a small adit that has been dug into a short mineral vein, which is marked on the British Geological Survey map, where the rhombohedral habit of the crystalline calcite above it is quite obvious.
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| An adit dug into a calcite vein |
Although there is a long history of lead mining along Lathkill Dale, we didn’t see any galena, fluorite or barytes, which are very often associated with the rakes of Derbyshire. We continued along another unnamed shallow dale, which is tributary to Cales Dale, until we reached One Ash Grange – a settlement that was formed by the Cistercian monks of Roche Abbey in 1147.
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| Views of One Ash Grange |
I didn’t see anything in the various agricultural buildings that suggested such an ancient history; however, I thought that the Grade II Listed C18 pigstyes are quite spectacular – especially since large slabs of Carboniferous Limestone, instead of sandstone, have been used for their flat roofs, which I had not seen before.
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| A detail of the pigstyes at One Ash Grange |
We finished the day by taking the public footpath from One Ash Grange back to the southern edge of Lathkill Dale, where we got another view of the Ricklow Quarry, before continuing along the path that drops into the dale and back to our starting point.
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| A view of Ricklow Quarry |
Having got back to Sheffield, with half an hour to wait for my bus back to Treeton, I took advantage of the late afternoon sunshine by enjoying a very welcome pint of beer at a great traveller’s rest, the Old Queen’s Head.
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| A pint of beer at the Old Queen's Head |
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