Geology in the Shirtcliffe Valley

Alternating fine sandstone and siltstone

Following the bridleway from Handsworth to Myrtle Bank Farm, after having a quick look at the old vicarage at St. Mary's church, I was glad to have brought the map that was sent to me by Pat Howells of the Friends of Shirtcliffe, which showed the public rights of way through the farmland.

 

A map showing public rights of way

Stopping a few times to get my bearings and take a few photographs of the landscapes that I could see in the distance to the east and south-east, I eventually arrived at the bridleway that runs along the north side of the Shirtcliffe Valley.

 

A view from Myrtle Bank Farm

During our meeting a few weeks earlier, Pat had told me that there was an old quarry alongside the bridleway and, having identified an area of rock exposures on an online Ordnance Survey map, which I assumed was this quarry, I put my map away and went in search of it.

 

A bridleway in the Shirtcliife Valley

Continuing along the bridleway, and looking for rock outcrops in the ground above me, I saw a vegetated, near vertical slope that I thought looked man-made rather than natural but, looking at old Ordnance Survey maps, no quarries have been recorded here; however, having subsequently discovered the British Geological Survey 1:50,000 maps online, this area is marked as being previously excavated ground.

 

Steeply sloping ground

Walking past similar slopes for a couple of minutes, which were covered in dense undergrowth that made it difficult to explore these, I occasionally saw subtle changes in the slope and vegetation that hinted at exposures of bedrock beneath the covering of soil.

 

Bedrock hidden beneath the soil

Finally, I came across a discontinuous exposure stretching for a few metres, where there is a succession of alternating thinly bedded sandstones and siltstones, with the upper section of sandstone being undercut to leave an overhang.

 

An exposure of sandstones and siltstones

In the lower section that is exposed here, graded bedding with fine sandstone passing upwards into siltstone can be quite clearly seen, with differential weathering of the softer siltstone leaving a series of small ledges.

 

Differential weathering of sandstone and siltstone

 

The sandstone here is a continuation of the Woodhouse Rock, which I had already seen well exposed at Drakehouse Rocks, the Mosborough Parkway and in the historic buildings of Woodhouse – as well as sporadically in the banks of Shirtcliff Brook.

 

The geology around the Shirtcliffe Valley

 

The minor sandstones in the Pennines Coal Measures Group are subject to rapid changes in grain size, both vertically and laterally, which reflects their mode of formation as minor river channels, crevasse splays, overbank deposits and lacustrine deposits.

 

Undercut sandstone

A little further on from this exposure, a small area of open ground is littered with small angular fragments of more massive sandstone, which again suggests that these are the product of quarrying activities – perhaps for simple boundary walls - and not natural.

 

Open ground littered with angular fragments

On an overcast day, the piece of sandstone that I collected looks distinctly brown when held in the hand and, seen through the hand lens, comprises fine grains of angular quartz, with a high proportion of very dark brown grains that are probably iron bearing minerals.

 

A sample of Woodhouse Rock