Tuesday 29 September 2020

Charnwood Forest - Part 3


Hill Hole Quarry

Leaving the car park at Billa Barra Hill Nature Reserve, having explored Billa Barra Hill and New Cliffe Hill Quarry during the reccy for the forthcoming field trip to Charnwood Forest with the Sheffield U3A Geology Group, we then set off on a short drive to the village of Markfield.

A notice board at the car park

Parking at the Hole Hill Nature Reserve car park on Hill Lane, we walked down the path alongside some fine allotments until we came across a path up to the edge of Hill Hole Quarry, which is the type locality for the Precambrian granophyric diorite known as markfieldite.

A notice board at the viewing point

To our great surprise and amusement, the viewing point was occupied by a few locals who were spending their Saturday afternoon drinking a few beers and using the nature reserve as a golf driving range.

Hill Hole Quarry

After chatting with them for a while, and seeing enough of the quarry faces from afar to note the points of interest, we walked back down to the village where I quickly took a few photographs of the church of St. Michael and All Angels.

The church of St. Michael and All Angels

Dating back to the C12, the oldest visible part is the C14 tower and the church was restored in 1856, with a new north aisle added and many windows replaced at the same time. Unsurprisingly, it is built out of irregular blocks of markfieldite, with Carboniferous sandstone quoins and dressings, and the diorite is also used for large buttresses to the north churchyard wall.

Buttresses in the churchyard

Looking up at the various roofs to the north elevation, I could see that at least two different types of roofing slate have been used at various times. I didn’t get any close up photos of the details but I though that some of the roofing slate might be Swithland slate, which was once quarried at nearby Groby and at Swithland and Woodhouse Eaves a few kilometres to the north.

The Cambrian Swithland Formation comprises purple to grey meta-mudstones and greywackes with thin conglomeratic sandstones and it was used from Roman times as a roofing material and at the height of the industry, supplied slate for the roof of St. Pancras railway station in London.

The north elevation of the church

During the formation of the Charnwood Anticline, a weak cleavage was imposed on the rocks of Charnwood Forest but Swithland slate does not split well land the slates have rough surfaces and a range of thicknesses and sizes, with the largest being used for the courses above the eaves.

A Swithland slate roof

Although quarrying in Swithland continued to the late C19, the development of the canals and railways spurred the expansion of the Welsh slate industry, whose cheap, uniformly sized slates soon superseded Swithland slate as the preferred roofing material in this region.

The lychgate roof

Good examples of immediately recognisable Swithland slate can be seen in the lychgate to the church and also to the brick house that is set immediately next to it but, with time starting to move on, we didn’t further explore the village to see if we could find further examples of its use.

The war memorial

Before setting back to the car, we briefly stopped at the markfieldite war memorial, where the coping stones are made of a green banded stone that reminded me of the tuffs of the Borrowdale Volcanic Group in the Lake District; however, as I soon discovered at Altar Stones Nature Reserve, this was another example of the Bradgate Formation.

A detail of the war memorial


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