Wednesday, 23 June 2021

A Field Trip in Conisbrough - Part 4

A view to the west from Conisbrough Viaduct

Continuing with my exploration of Conisbrough, for a proposed field trip with the Sheffield U3A Geology Group, when making my way down the angled retaining wall at the outcrop of glaciofluvial sandstone at Constitution Hill Bridge, I had to consider how the group would cope with this incline.
A view down the angled retaining wall

Since joining the group in 2015, I had been out with them to numerous places where the vast majority of the members had tackled some steep climbs up rocky and uneven slopes but, although the study of geology necessarily entails exploration of such terrain, the U3A now require a risk assessment to be made for field trips.
Constitution Hill in February 2007
Having made my way safely back down to the track, I carried on eastwards towards the railway tunnel, which is at the east end of the site. During previous visits, I had found further clearly visible exposures of readily accessible glaciofluvial sandstone and beds of limestone, which have excellent examples of flowstone and calcite crystals on the exposed joint planes.
Calcite crystals on a joint plane as seen in February 2007

On this occasion, however, even though I had previously visted during September in 1997 and then during February in 2007, with the latter being the optimum time of the year to see bedrock, there were no obvious rock outcrops anywhere.
A view along Conisbrough Viaduct

In winter, the exposures may be much better exposed or a preliminary visit with gardening tools before a field trip may reveal some of the features that I had identified but, for now, I just carried on to Conisbrough Viaduct, which is built with the renowned Staffordshire Blue engineering bricks.
A view towards Cadeby Quarry from Conisbrough Viaduct

To the north, there are glimpses of the entrance to Cadeby Quarry, which contains a Geological SSSI - the type locality for the Cadeby Formation - and is now the major supplier of this dolomitic limestone. Although building stone was once widely quarried along the length of the Magnesian Limestone outcrop, it is now only available from a very few places.
A view east from Conisbrough Viaduct

On the east bank of the River Don, the waste stone from one of the old quarries that are found along this section of the Don Gorge can clearly be seen. Unlike others nearby, which are densely overgrown with vegetation, this quarry was active until quite recently and the spoil is still fresh.
A view to the north-east from Conisbrough Viaduct

Continuing across the viaduct, there are good views of the surrounding landscape and, although not illuminated by the afternoon sun, the escarpment on the Conisbrough outlier – known locally as The Crags – can be seen in the distance to the west and the keep of Conisbrough Castle is just visible above the surrounding trees.
A view of Conisbrough Castle keep from Conisbrough Viaduct

Having crossed the viaduct, I found a path that I had not traversed before and, instead of taking a diversion and following this eastwards to the Nearcliff Wood Quarries, which I would include in my field trip, I was more concerned with finding the best route back to Conisbrough.
A rock exposure next to the public footpath to Conisbrough

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