A Geological Recce in Cressbrook Dale

 

A view east along Cressbrook Dale

The Sheffield U3A Geology Group October field trip to Wincobank and the Thundercliffe Grange quarries proved to be the last day out of note in 2023, with November coinciding with the beginning of an exceptionally wet winter - the 8th wettest on record. 

 

At Sheffield General Cemetery

 

Although the Group convened at Sheffield General Cemetery in November, which I had helped my friend Catherine to prepare, half of the attendees left at lunchtime – on the grounds that it was too cold. Quite unusually for me, I had been suffering from a bad cold and feeling quite unwell and when one member made an inappropriate comment – after coming back from the pub whilst the rest of us ate their packed lunched in the cemetery – I was none too pleased.

 

Headstops at Kenwood Hall Hotel

 

At that point, I decided that I had also had enough for the day and, after taking the remaining members of the group to the Kenwood Hall Hotel, which was the highlight of the planned afternoon walk, I brought the day to a very early end. 

 

At the 2024 indoor meeting of the Sheffield U3A Geology Group

 

With the wet weather continuing through November to January, the next time that I left my house to do anything except essential shopping was to attend the Group indoor meeting at the Burton Street Foundation in Hillsborough, when my input was a talk on the building stones of Sheffield and the provisional field trip itinerary for 2024 was discussed.

 

Cressbrook Dale and Tideswell Dale

 

On the agenda for February was Cressbrook Dale and the Tideswell Dale quarry, which I had inspected back in 1995, as part of my assessment of the geotourism potential of RIGS (Regionally Important Geological Sites) in the Peak District National Park; however, a route still had to be devised and I was waiting for Paul to contact me to arrange a recce. 

 

The geology around Cressbrook Dale and Tideswell Dale

 

A few days before we were due to undertake our field trip, I received a phone call from Paul, who had spent 2 weeks on holiday in Lanzarote and subsequently sustained an injury at home that turned out to be a broken toe, to ask if I could go out on the Sunday to do the recce. 

 

The path to Cressbrook Dale at Wardlow Mires

 

I was glad to get out of the house after weeks of bad weather but, after being picked up from Treeton, the roads from Sheffield were unusually congested and, finally arriving at Wardlow Mires to start our recce, we immediately discovered that the beginning of the path was under water. 

 

An outcrop of the Eyam Limestone Formation

 

Making our way alongside a dry stone wall and then continuing past an outcrop of what I think is the Eyam Limestone Formation, which we didn’t stop to examine, Paul was clearly struggling and we slowly continued along the path until Peter’s Stone – a good example of a translational landslide - came into view.

 

Peter's Stone

 

When I visited Cressbrook Dale in 1995, I was struck by the corals in the Monsal Dale Limestone Formation and the cemented scree on the north side of what is normally a dry valley at this location, but the water table had risen so much that we would now need waders to cross what was now a deep stream. 

 

The effects of a rising water table on a normally dry valley

Carrying on along the path, I was very interested to see that in a couple of places, water was gushing out from the hillside along a temporary spring line, where the permeable limestone comes into contact with the Cressbrook Dale Lava. 

 

A spring formed at the junction of limestone and basalt

 

At this point, I walked quickly ahead along the footpath on the bottom of the valley to look for signs of the Cressbrook Dale Lava and the Litton Tuff, which lies several metres above it. There was no obvious features to indicate their presence, except perhaps a small area where brown soil was revealed on the upper slope, so I walked back to meet Paul on a less well defined footpath at a slightly higher level. 

 

A possible exposure of weathered Litton Tuff in the hillside

 

Although I didn’t notice anything from the lower path, looking down at this path, it was immediately obvious that the lava was exposed along its length for several metres and sporadically at slightly higher and lower levels. 

 

The exposure of the Cressbrook Dale Lava

 

With my Estwing hammer, I was able to prise a loose piece of rock from below the path, which I then split into two. The specimen comprises amygdaloidal olivine basalt, with the calcite infilling the vesicles standing out against the very dark green groundmass, in which I can’t clearly see any individual crystals of mafic minerals or plagioclase feldspar. 

 

A specimen of Cressbrook Dale Lava showing amygdales

 

Having met back up with Paul, we retraced our steps and then slowly made our way up the grassy slope to the smaller slipped block of the Monsal Dale Formation, which is positioned beneath the much larger Peter’s Stone and shows marked tilting of the beds. 

 

The walk up to Peter's Stone

 

Taking care not to step into the voids around the edge of some of the outcrop, we managed to find good examples of Lithostrotion corals, but there were no signs of the solitary rugose corals Dibunophyllum or Diphyphyllum, which have been identified in the Hob’s House Coral Band - a distinctive marker horizon that is found in Peter’s Stone and the scar in the main outcrop. 

 

Lithostrotion corals

 

Ascending a little further to the base of Peter’s Stone, a quick search among the various sized blocks that form a deposit of scree revealed further examples of corals and brachiopods, include a medium sized piece of limestone that displays a bed that contains several brachiopod moulds.

 

A block showing brachiopod moulds along a bedding plane

 

Looking towards Wardlow Mires from Peter’s Stone, we obtained spectacular views of Cressbrook Dale and the extent of the flooding of the valley bottom and, having managed to find a few features of interest for our field trip, we returned to the car.

 

A panoramic view along Cressbrook Dale from Peter's Stone

 

We then drove to the Tideswell Dale car park, to look at the spheroidal weathering of the dolerite in the small quarry at its entrance; however, it was obvious by now that Paul would be unable to participate in our field trip three days later and our recce came to an end, without the Tideswell Dale quarry being visited or Tansley Dale - an essential part of the walk – being explored. 

 

The small quarry at Tideswell Dale car park