Geology in Canklow Wood - Part 2

 

Small scale deformation in the Rotherham Red sandstone

 

Continuing with my exploration of the old Rotherham Red sandstone quarries in Canklow Wood, I came across several more examples of massive beds of sandstone with large scale cross-bedding, which record the movement of sediment in a large river channel.

 

Flaggy beds above massive sandstone

I could also see that the upper parts of these were composed of thinner flaggy beds, which can often be seen in the upper parts of exposed rock outcrops, where the surface weathering processes that lead to the formation of the soil horizon are operating.

 

Flaggy beds above massive sandstone

Looking closer, the massive sandstone is seen to pass upwards into the thinner planar beds, without any discernable break in the deposition of the sediment. They also have low angle cross-lamination and are consistent with deposition with in the upper flow regime of the channel, where the rate of flow of the water is greater.

 

An abrupt change from massive to flaggy sandstone

In places, there is a very abrupt change from massive beds with large scale cross-bedding to finer grained, thin bedded flaggy sandstone, where there is a very distinct break in the bedding, which marks a period of erosion.

Diffferential weathering produces overhangs

Looking around the old quarry, various other interesting features can be seen, including graded bedding in the more massive beds, with the finer silty sediments being differentially weathered to leave distinct overhangs in places – features that have appeared in the faces since quarrying ceased in the C19.

 

Cross-bedding and differential weathering

These old quarries were identified as a Regionally Important Geological Site, when surveyed by the South Yorkshire RIGS Group back in 1997 and, although they never received the same attention as the nearby Boston Park, they contain a wide range of sedimentary structures – including trough cross-bedding, which is associated with the migration of large sub-aqueous sand dunes along the river channel.

 

Trough cross-bedding in massive sandstone

Having had a good look around the various exposures of this red variety of Mexborough Rock, where I collected a couple of specimens of sandstone that show various degrees of red colouration, I made my way up to the path that runs along the escarpment.

 

Specimens of Rotherham Red sandstone

Looking down through breaks in the covering of trees, I could see glimpses of rock in other quarry faces that were not easily accessible across mounds of waste stone and then continued along the path through the Canklow Hill earthworks, which is a Scheduled Monument, but seeing no obvious evidence of these I carried on to Boston Park. 

 

A view of an overgrown quarry