 |
| A view up Tansley Dale |
On a warm and sunny last day of April 2024, having not been out since my circular walk that included All Saints churchyard, an exploration of the building stones of Bents Green, a walk to Whirlow and then back to Ecclesall, I set out with my friend Stuart, who had co-led a field trip with me to the High Peak Trail a couple of years earlier, to undertake a recce for the June 2024 Sheffield U3A Geology Group field trip.
 |
| The circular route from Litton via Tansley Dale and Cressbrook Dale |
I had previously undertaken a recce in February, which was cut short due to the fact that the valley was flooded after a period of exceptionally wet weather and that the group leader Paul, who I went with, had sustained an injury a few days before that turned out to be a broken toe.
 |
| The first stile on the path from Litton to Tansley Dale |
Arriving in Litton and checking the availability of parking, our first task was to assess the accessibility of the first two stiles on the route. Before the recce, I had contacted a Peak District walking group to ask if the water levels in Cressbrook Dale had subsided and someone had responded to tell me that she had found these quite difficult to negotiate without assistance.
 |
| The second stile on the path from Litton |
Most of the group members are in their 70’s and, although they need to have a decent degree of mobility and fitness to cope with the terrain that is typically encountered on a field trip, the U3A have increasingly emphasised that field trip leaders must undertake formal risk assessments and more - just one of the factors that has certainly led to my diminishing interest in this organisation.
 |
| The public footpath from Litton to Tansley Dale |
Having agreed that these stiles wouldn’t present a problem for our members, we continued for a few hundred metres until we reached the head of Tansley Dale. I had never heard of this dale before but, when undertaking preliminary research, I discovered that it is a Scheduled Monument with descriptions of the former lead mining industry here being provided by Historic England and the Derbyshire Historic Environment Record.
 |
| The approach to Tansley Dale |
When the upper part of Tansley Dale came into view, I could clearly see the disturbed ground but Stuart, who had written his dissertation on lead mining in the Peak District as part of his joint honours geology and geography degree, was able to point out many more features.
 |
| A view down Tansley Dale |
Continuing down Tansley Dale past the foundations of walls and waste rock that have largely become overgrown, on either side of the valley there are several entrances to adits which coincide with the position of the lead rakes on both sides.
 |
| An entrance to an adit |
The 1:50,000 British Geological Survey map shows that a series of rakes run west to east over from the head of Tansley Dale, which continue for a distance of nearly 5 km and workings on these are clearly visible on LIDAR maps.
 |
| The geological map showing the lead rakes in and near Tansley Dale |
Alongside the path, there are several small outcrops of the light facies of the Monsal Dale Limestone Formation (MDLF), which are shallow shelf deposits that very often contain brachiopods and corals. We did not notice any fossils, but there was an opportunity to take a measurement of the strike and dip on the exposed bedding planes, which Stuart compared to the measurements that are recorded on the maps that he had brought with him.
 |
| Measuring the strike and dip |
Immediately above the first adit that we encountered, a thick layer stands out as having a very rough and irregular texture that contrasts with the limestone above and below it. Getting close enough to touch it, the photo that I took shows what look like shrinkage structures that are orientated at right angles to the outcrop.
 |
We didn’t reach any conclusion about what we were looking at but, enlarging one of my photos, I can see rhombohedral cleavage, which is typical of the mineral calcite and suggests that this is part of the mineral vein that the lead miners were exploiting.
 |
| Examining calcite in a mineral vein |
Continuing down the path past small areas of waste rock that are composed of lumps of the unfossiliferous dark facies of the MDLF, which was formed offshore in much deeper water, our next stop was an incongruous relatively level feature that was not natural and Stuart immediately recognised this as the main waste tip.
 |
| A view down Tansley Dale while standing on the edge of a waste tip |
My botanical knowledge is not great, but I know just enough to able to recognise wild orchids when I see them and, as I later discovered from the information panel at Tideswell Dale car park, the early purple variety were flourishing on the ground that had been undisturbed by lead mining.
 |
| An early purple orchid |
Making our way down to the end of Tansley Dale and looking back up the valley, another adit can be seen high up the hillside on its north side, with the position of the rake being marked by a linear feature of excavated ground above and below it.
 | |
| A lead rake at the east end of Tansley Dale |
No comments:
Post a Comment