Geology in the Upper Don Valley

A 3D view of the geology in the Upper Don Valley

When studying geology at Nottingham University, an essential part of the training was to learn how to interpret and make geological maps, which for me entailed six weeks exploring the Borrowdale Volcanics, near Derwentwater in the English Lake District. 

1:50,000 British Geological Maps of South Yorkshire and adjoining areas

Although I was commended for my mapping project, I knew that I wasn’t destined for a career with this and I haven’t used a compass clinometer ever since; however, having subsequently surveyed numerous sites in the Peak District National Park and South Yorkshire – highlighting their conservation, educational and aesthetic value - the printed British Gological Survey maps and accompanying memoirs that I own have been invaluable. 

British Geological Survey Memoirs to accompany 1:50,000 scale maps

Looking at the 1:50,000 scale map of Sheffield, I have often scratched my head when trying to work out the structure of the region, with various faults and folds affecting the Upper Carboniferous strata – especially the Don Monocline, which has tilted the rocks more than 30 degrees in places.

An extract from the old printed 1:50,000 geological map of Sheffield

The rocks here were distorted during a period of mountain building known as the Variscan Orogeny and the precursors to the River Don and four other rivers have cut into them to leave a landscape in Sheffield that has often been described as having seven hills – with distinct valleys in between. 

The Upper Don Valley on the Geology of Britain Map Viewer

Having explored some of the hilly green spaces that are part of the Sheffield Round Walk and, afterwards referring to geological maps of the areas - including the 3D Geology of Britain Viewer - I begun to get a much better appreciation of the structure of the rocks – even though I had encountered very few rock outcrops. 

An outcrop of Greenmoor Rock on Brincliffe Edge

With the very mild and often sunny weather continuing well into the autumn of 2018, I resumed my investigations in the Loxley Valley and around Chelsea Park on Brincliffe Edge – where there are still occasional outcrops of Brincliffe Blue/Greenmoor Rock relating to the former quarrying industry here - and looking on Google Map I decided to visit Crookes Valley Park, which I had noted when working as a geologist at Weston Park Museum. 

A dry stone wall built on Greenmoor Rock in Mushroom Lane

Starting my walk on Mushroom Lane, the first thing that I noticed was that the boundary wall opposite the museum contained, in its lowermost parts, small outcrops of flaggy Greenmoor Rock upon which the dry stone wall has been built.

A detail of bedrock and dry stone walling on Mushroom Lane

This tiny rock exposure doesn’t provide enough surface area on the bedding planes to take an accurate measurement of the dip and strike of the strata, but the visible inclination of the laminated beds reflects the effects of the Don Monocline – with a dip of 25 degrees to the south-east measured by the British Geological Survey here. 

Rising ground formed by the Loxley Edge Rock in Crookes Valley Park

Mushroom Lane slopes down in a north-easterly direction towards the River Don and, to the north-west, a distinct escarpment drops down into Crookes Valley Park – now filled with a reservoir – with the land rising again along the dip slope of the older Loxley Edge Rock, which again dips more than 25 degrees here. 

A view south-east across Crookes Valley Park to Weston Park Museum

Arriving at Crookes Valley Road, the infilling of the dams that occupied this valley from the 18th-19th century, and the subsequent landscaping to build this road, detract from the natural lie of the land – which includes a sharp change in the topography that coincides with a fault, as I had previously experienced when going to an event in The Ponderosa the year before. 

Crookesmoor Road follows the Grenoside Sandstone down to the River Don

Walking up Crookes Valley Road to the junction with Crookesmoor Road, the relationship between the geomorphology and the geology started to become more obvious – especially when I walked down the long straight road to Upperthorpe, with views over The Ponderosa to my right. 

Views up Blake Street towards Ruskin Park

Having by now orientated myself with the stretch of the River Don that runs from Lady’s Bridge to Hillsborough, I began to find my way to Ruskin Park, a green space that I had identified on Google Map when planning this day out. Winding my way up through a few residential streets, where I unexpectedly encountered Blake Street Nature Park, I then came across Blake Street itself, which – I learned shortly after – is Sheffield’s steepest street. 

Various views down Blake Street towards Sheffield city centre

The steep slope again is controlled by the structure associated with the Don Monocline and, when walking up the street, the Greenmoor Rock is succeeded by the younger Crawshaw Sandstone. At the top of Blake Street, the topography flattens out, with an inlier of the Rough Rock being exposed at the surface by a fold that plunges east to the River Don, before the strata dips down towards the River Rivelin in the north. 

A view of Parkwood Springs from Ruskin Park

From the vantage point of Ruskin Park, views of the old quarry faces adjacent to the landfill site at Parkwood Springs can be seen on the other side of the Upper Don Valley. Here, the escarpment that comprises mainly Greenmoor Rock has been widely exploited for building stone, ganister for making refractory products and for brick making. 

A detail of an old quarry face at Parkwood Springs

Now the subject of a planned phase of major regeneration by Sheffield City Council, this area contains two Geological Sites of Special Scientific Interest and, from various public paths that cross Parkwood Springs, various points of geological interest are clearly seen. 

A view of Parkwood Springs from Albert Terrace Road

Having spent less than an hour and a half exploring a part of Sheffield that I didn’t know, I finished off my walk at Penistone Road, where I took a few quick photos of the Neepsend Brick Pit SSSI, before heading back to Sheffield city centre on the tram – where I had a quick look around the exterior of Sheffield City Hall.

A view of the Neepsend Brick Pit SSSI from Albert Terrace Road