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| A high level exposure of flaggy sandstone |
After making my way down to Thundercliffe Grange, via a circuitous route through Grange Park, the path running along the base of the escarpment at Barber Wood was well marked and, after a short distance, I found the sandstone quarry that I had briefly inspected back in 1996 for the South Yorkshire RIGS Group.
I had expected it to be quite overgrown after such a long time but, although saplings have begun to occupy the quarry floor, it was pretty much as I remember it, with several faces of sandstone being exposed. Although a minor unnamed sandstone lying between the Penistone Flags (PF) and the Silkstone Rock (SR), it forms a prominent topographic feature.
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| A small squarry to the east of Thundercliffe Grange |
Seen from a distance, the light brown sandstone looks quite massive, with no well defined pattern of jointing on the quarry face, but having noticed one area where there is a zone of narrow joints parallel to the quarry face, I went to have a closer look.
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| Jointing parallel to the quarry face |
Here, an exposed angle on the quarry face has weathered away to reveal a section of very thin cross-laminated beds, where a high concentration of iron gives the sandstone a distinct orange colour – a characteristic that can be seen in very many of the blocks of stone used in Thundercliffe Grange, which were quarried locally.
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| An exposure of ornage cross-laminated sandstone |
The sample that I took with my Estwing hammer is fine grained, light brown in colour with feint iron staining that is concentrated into a dense, less than 2 mm thick band of iron oxides/hydroxides on one of the fresh surfaces.
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| A sample of sandstone from the quarry east of Thundercliffe Grange |
Continuing along the path at the lower edge of Barber Wood, I came across a barred entrance to another much larger quarry, which wasn’t on the list of potential RIGS to survey and where I immediately noticed that the upper section of the quarry face comprised very flaggy beds.
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| Flaggy sandstone in the quarry south-east of Thundercliffe Grange |
Very often, the Pennine Coal Measures Group sandstones are seen to pass up upwards from massive to flaggy beds, which reflects the flow regime in the river channel in which they are deposited. Where exposed at the surface, the sub-aerial weathering processes that break down the rock exploit these bedding planes and the subsoil is usually well developed.
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| An exposure in the quarry south-east of Thundercliffe Grange |
The access to the high level flaggy sandstone wasn’t very easy and I didn’t try and obtain a specimen of this. Although only an associate member of the Sheffield Area Geology Trust and I therefore no longer officially contribute to the designation or management of geological sites in South Yorkshire, as with the problem with the litter at Maltby Crags, I just took a few photos of the burnt out cars that had been dumped in this quarry to send to the relevant authority.
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| A burnt out car |
Continuing along the path, the escarpment formed a persistent topographic feature and, although a LIDAR map indicated that there were further small workings, I didn’t see any good exposures and therefore carried on until I reached Ockley Bottom.
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| A view along the escarpment in Barber Wood |
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