A Geology Lesson at Waverley

 

Various rocks collected from the Waverley Estate (21mm coin)

Since living in Treeton, following the full remediation of the former Orgreave opencast coal mine in 2011, I have seen the Advanced Manufacturing Park and the Waverley Estate develop at a great pace and, on occasion, I have wandered around these sites to find various Coal Measures rocks that have differentially weathered – according to their physical and chemical composition. 

 

Bioturbated siltstone

 

After my last visit in December 2021, when I encountered further examples of these – as well as glacial erratics composed of basic migmatite in the play area and pebbly Millstone Grit to decorate the streets - I posted my photos on Facebook and had responses to say that these various rocks could be used as the basis of a simple lesson in geology. 

 

A basic migmatite glacial erratic

 

Knowing that Waverley Junior Academy had opened quite recently, I made a call to the editor of the Wave community magazine, who told me that his children attended this school and was very interested in my ideas; however, I didn’t get round to doing anything about this at the time but, after the Sheffield U3A Geology Group March 2023 field trip to look at the urban geology of Sheffield, I phoned the editor again and was surprised to learn he was still interested in a short article being written for the magazine.

 

A geological map showing the Orgreave opencast coal mine © BGS

The Orgreave opencast coal mine exposed the Pennine Middle Coal Measures Formation strata between the High Hazles Coal and the Aegiranum (Mansfield) Marine Band which, although containing a few thin minor sandstones, comprised mainly mudstone and grey siltstone with other coal seams and black shales. 

 

A section of the geology exposed in the Orgreave opencast coal mine © BGS

 

In the 12 years since the deep open pit had been refilled using the vast pile of waste, which prevented St. Mary’s church in Handsworth being seen from St. Helen’s church in Treeton, the lumps of mudstone and shale that were quite common in the landscaping have now mostly weathered to small fragments, but these and small pieces of coal can still be found. 

 

Blocks of grey siltstone

 

The large blocks of grey siltstone that were retained, however, have been used to block vehicular access to the site and have been moved around as the development has progressed. In these, carbonaceous and iron rich beds and rippled surfaces with bioturbation are often seen, which all provide interest to the geologist and, as I discovered when popping briefly into the school, the teacher that I met also seemed to be very interested. 

 

A band of clay ironstone nodules in a block of grey siltstone

In one of the blocks at the corner of Rivelin Way and Derwent Chase, a well developed bed of clay ironstone nodules is clearly visible and, one side of the block, the siltstone has crumbled away to reveal well preserved plant stems – a type of fossil that that I had never encountered before and which I think is well worth seeing. 

 

Fossil plant stems in a block of grey siltstone

 

Continuing my walk around to Cherry Wood Way, the developer that was now building on the land to the west of the River Rother had obviously been redistributing the landscaped rock waste, to accommodate their housing scheme, and I went to investigate a part of this that was easily accessible from the roadside. 

 

A view from Cherry Wood Way

 

In addition to a few ironstone nodules that had weathered out of the siltstone, I was very surprised to encounter a large number of pebbles of various sizes and composition that are very similar to those that I collected a couple of years earlier, when walking from South Anston to Kiveton Park and then from Todwick to Wales. 

 

An ironstone nodule

 

On that occasion, I had been crossing a small area that had been marked as Quaternary till on the geological map, even though it only consists of a scattering of various pebbles on the surface of the ploughed fields, which surround the public footpath that I was following. 

 

Pebbles of sandstone and quartzite

 

Along with glaciofluvial pebbles, which often include white vein quartz and purple quartzite, these are more commonly found on higher ground on interstream areas on the Magnesian Limestone and are not common on the Coal Measures, where the mudstones have been more easily eroded. 

 

A gritstone pebble

 

In this part of Rotherham, the geological memoir records that grave diggers in Moorgate Cemetery encountered 3 metres of greyish-brown mottled clay with rounded pieces of quartzite and blocks of sandstone and a much larger expanse occurs either side of the Bawtry Road in Brinsworth. 

 

Outcrops of glacial till in the vicinity of Waverley

 

It is therefore conceivable that such sporadic deposits existed on the land that has been mined away, only to turn up again on the surface in a very random way, as part of the subsequent redistribution of the landscaped heap of coal waste. 

 

A block of conglomerate

 

Having found numerous pebbles that I thought must have a glaciofluvial origin, I was even more surprised to discover a large piece of what looks like a conglomerate, which appeared amongst large lumps of concrete, a pile of limestone aggregate and blocks of grey siltstone. 

 

Views of the conglomerate from the top and side

 

Composed of an unsorted mass of imbricated subangular to subrounded clasts of sandstone, it reminded me very much of a similar cemented glaciofluvial deposit at Constitution Hill (grid reference SK 51713 99601), north of the River Don at Conisbrough railway station, which I had highlighted in the Doncaster Geodiversity Assessment (pp.55-60) and was one of the key sites for a proposed field trip with the Sheffield U3A Geology Group. 

 

A Geology Lesson at Waverley

 

Now having plenty of varied specimens of rock from Waverley, with numerous photographs of the large blocks of rock that I had encountered, I returned home and immediately set about writing a short article for the April/May 2023 issue of the magazine.

 

The front cover of the April/May 2023 issue of Wave