A Return to the Porter Valley

Peter Kennett with a geological map of the Porter Valley

At the beginning of spring 2017, as part of my exploration of the Sheffield Round Walk, I planned to walk from Ringinglow down the Porter Valley into Endcliffe Park, stopping off at various points of interest highlighted in the leaflet – The Geology of the Porter Valley. 

Due to problems with the bus service, which resulted in me having to walk from Whirlow up to Ringinglow via the Limb Valley, beforehand, I didn’t have the time or inclination to stick to my plans; however, I got another chance to look more closely at the Porter Valley, when Peter Kennett himself led the Sheffield U3A Geology Group there on the last field trip of 2018.

A discussion about Carboniferous flora and fauna

Meeting up on a cold November morning, more than 20 of us convened at Forge Dam, where we were given an introduction to the geology of area, using various maps, 3D models, photographs and maps that Peter had accumulated when teaching geology at the nearby High Storrs school. 

The group stops to look at a monocline in the river bank

We then followed the meandering Porter Brook downstream to a point where the sandstone in the Rough Rock has been folded into a monocline that can be seen in the river bank, before walking further along the brook to another exposure of the Rough Rock, where large scale cross bedding is evident in the river bank. 

An example of large scale cross bedding in the river bank

Like Ecclesall Woods and other locations on the Sheffield Round Walk, none of the rock exposures were very spectacular, but the various dams, goits, weirs and iron stained tributary springs and streams record some of Sheffield's industrial history - which was very dependent on the geology and geomorphology. 

A fossil mould of a Lepidodendron root

Walking a little further downstream, we stopped to look at a small exposure of the Rough Rock which contained fossil moulds of the roots of a primitive tree from the Carboniferous Period – known as Lepidodendron. 

An exposure of Rough Rock at Porter Bridge

Continuing past Porter Bridge, more flaggy sandstone in the Rough Rock could be seen in the bank where branches of the Porter Brook merge here and, less than 100m from this point, the boundary between the Millstone Grit and the Lower Coal Measures has been determined. 

A river bank exposure of the Pot Clay and associated strata

The Rough Rock is succeeded by the Pot Clay, which is described in detail on page 36 of the Geology of the Country Around Sheffield memoir (1957) but, at the time of our visit, the water level was far too high for us to see the various strata mentioned. 

An electric transformer on Highcliffe Road

From here, we retraced our steps to Porter Bridge before walking up Highcliffe Road on the south side of the Porter Valley, where we encountered an old electric transformer, before being told about the various shallow coal workings that are found around here - including drift mines and bell pits. 

An explanation of the mining of coal with a bell pit

After what proved to be a very short day out, compared to the last field trip that I had undertaken with the Sheffield U3A Geology Group, we then made our way back down to Forge Dam – making various observations and comments on points of interest that we all saw on the way.

Modern sculpture