Further Surveys of the Greenmoor Rock

Spheroidal weathering and Liesegang rings at Heeley Retail Park

During my brief exploration of Totley, I discovered an escarpment of the Greenmoor Rock that I had never seen before. Although I didn’t see any rock exposures, and had to rely on the vernacular buildings to give me an idea of its physical characteristics here, it provided further insight into its importance - in contributing to the landscape and economy of Sheffield. 

The outcrop of the Greenmoor Rock between Norton and Brincliffe Edge

Having encountered the Greenmoor Rock many times when exploring Sheffield in the last couple of years, I thought that it might be possible to base a future field trip with the Sheffield U3A Geology Group on the sites that I had visited. 

Sites visited to examine the Greenmoor Rock

When visiting the church of St. James the Great in Norton, roughly following the route of the Sheffield Round Walk, I walked through Graves Park a couple of times and was interested to see that several spring fed streams converge here, before flowing down through Cobnar Wood. At the end of October 2018, I decided to go and take a closer look. 

Entering Cobnar Wood in Graves Park

Knowing already that the nearby Morrisons supermarket in Meadowhead occupies an old quarry, with accessible rock faces, I was interested to see how much rock was exposed and if it had potential as a field trip location. 

Mudstone exposed along the stream bank in Cobnar Wood

The strata between the Grenoside Sandstone and the Greenmoor Rock are composed of mudstone and siltstone, which the various streams in Graves Park essentially follow; however, after converging, a single brook runs down through a spectacular steep sided V-shaped valley that has been cut into the similar softer rocks beneath the Greenmoor Rock. 

A detail of mudstone

Although extensive rocky exposures of flaggy sandstone are rare, in many places where the banks of the brook have not been lined with stone walls, it is possible to see outcrops of the finely bedded mudstone and siltstone. 

A general view of Cobnar Wood

Leaving Graves Park at the Cobnar Road entrance, the brook disappears beneath a built up area before reappearing 150 metres further down the road, to the west of the steeply falling ground at the rear of the Big Tree public house.

An outcrop of flaggy sandstone in Cobnar Wood

I had previously walked down the A61 through Woodseats down to the Homebase/Dunelm site, which sits in another large old quarry – exploited for making bricks - where there are good exposures of the Greenmoor Rock and underlying strata, so I decided to try and follow the course of the brook down to the River Sheaf and see what I might find. 

A walk to Sheffield from Graves Park

Discovering that the brook largely flowed through underground culverts, I quickly made my way down to Abbeydale Road and headed back to Sheffield, but not before coming across the site of an old quarry that I had passed by many times in a car or on the bus. 

An old quarry face on Marden Road

Occupied by a petrol station as long as I had known it, and now the site of a car wash, the old quarry faces visible from Abbeydale Road are covered by concrete blocks that form a retaining wall. Turning into Marden Road, however, an extensive exposure of flaggy sandstone can clearly be seen, which I later discovered was another exposure of Greenmoor Rock. 

A detail of the quarry face on Marden Road

From here, a walk up and along the escarpment formed by Brincliffe Edge connects with several locations where the Greenmoor Rock is exposed in old quarries, which once supplied vast amounts of the local variety known as Brincliffe Blue, for general building, kerbs and setts and for high quality memorials. 

Greenmoor Rock at Brincliffe Edge

With my walk from Graves Park to Marden Road revealing two good sites for a potential field trip, my exploration of the Greenmoor Rock in Sheffield in 2018 finally came to an end in the week before Christmas, when I unexpectedly discovered another old quarry that is now occupied by the Heeley Retail Park – which I visited to buy a new DVD player in time for the holiday. 

An old quarry face at Heeley Retail Park

In the car park, in addition to exposures of flaggy sandstone there is an excellent example of spheroidal weathering and Liesegang rings, with an angular spur of sandstone being rounded off by the delamination of sheets of sandstone parallel to its exposed surfaces. 

An exposure of Greenmoor Rock at Heeley Retail Park

Also, at the junction of beds of sandstone with underlying mudstone, an artificial spring line has developed, where permeable and impermeable rocks meet. It makes a good stopping point between the exposures at Homebase/Dunelm and Marden Road and, with a short diversion along the way, to Meersbrook Park, a natural spring can be seen too.

A stream fed by a spring in Meersbrook Park