Geology in the Forest of Dean

Upper Soudley Geological Trail - Saturday 21st September

Near Upper Blue Rock Quarry

Here are some photos and a couple of pencil sketches of rock outcrops / former quarries seen along the Upper Soudley Geological Trail on the eastern side of the Forest of Dean in Gloucestershire. This was part of a Geological field trip in the area, organised by the WOUGS and led by Alan Holiday on Saturday 21st September. After the trail, we had lunch at the Dean Heritage Centre, before heading south to Beachley Point and Sedbury cliff, to look at rock outcrops along the Severn estuary near Chepstow and the Severn Road Bridge – see next entry. 

Particularly for late September, it was an exceptionally sticky Saturday, with little or no wind and temperatures in the high teens – low 20s degrees celcius. It was better near the estuary this afternoon, where there was some breeze, though it felt oppressive in the Forest, which had a close, hemmed in feel to it, anyway and no wind at all. In such weather, the cooked breakfast at the start of the day felt a bit much. Particularly near the start of the trail, the ground underfoot was very moist, a bit muddy in places. I preferred the cooler, much fresher weather we’d had on the north Pembrokeshire coast the week before.

Hod Boy Memorial

Taking the road through the heavily forested eastern side of the Forest of Dean – a mix coniferous and deciduous woodland, we headed towards the  Dean Heritage Centre at Upper Soudley. Here, we met some of the  WOUGS members, before going on to Upper Soudley village Hall. From there, we took a short walk through a residential area to the start trail, our leader. Pointing out a couple of houses built with the local Devonian Old Red Sandstone. 

The trail followed the track of a former railway line servicing the former mining and quarrying industries in the Forest. As Alan said near the beginning, part of the trail was very overgrown, so we didn’t see everything in the guidebook. Moving along it, the outcrops of rock became progressively younger: the Devonian Old Red Sandstone Series near the entrance to the trail to limestones of upper Carboniferous age further along. The big geological picture was a syncline, in which the beds are folded to form a trough in cross-section, with the youngest beds in the core. Some of these contain coal seams. These were once mined, though not on the scale of the coal fields in northern England. 

Tree Sculpture on the Upper Soudley Trail

As well as Geology, there were hints of the Forest of Dean’s industrial past. Between the first two rock outcrops we visited, we went down some steps to the Hod Boy Memorial, a poignant tree sculpture placed here in 2002, the year of the Queen’s Golden Jubilee.  It honoured the young boys who went down the mines, and very young they were. I suppose they wanted people small enough to squeeze along very claustrophobic narrow passages. In the Heritage Centre car park, there was another powerful image tree sculpture of two men in a mining rescue. This was one of the more serious sculptures amid a company of Gruffaloes ( as in the popular children’s stories by Julia Donaldson, illustrated by Axel Scheffler) and a praying mantis. I didn’t notice it on the way in, but on the way back along the trail at the end, I saw the carving of an older man sitting by what would have been the railway side here. 

Lined stream

Some of the streams were still lined with impermeable material to stop the water sinking down through the cracks in the Carboniferous Limestone.

The Upper Blue Rock Quarry and Shakemantle Quarry were interesting for me both from a rocky and arty perspective. At both, the beds were fairly steeply dipping, like the lower Palaoezoic sandstones and mudstones in Pembrokeshire. At Upper Blue Rock Quarry, up the hill from the track and into the woods, were two rows of archways, where quarry workers had cut in to the stone. A few loose blocks containing fossils - crinoids and a few corals. This quarry was set amid ferns and beech trees, rooted into the rock face.

Sketch at Upper Blue Rock Quarry

Shakemantle Quarry was high, a much more open rockface, with pine trees growing on the slopes. The greenery of the trees complemented the  pale pinkish grey of the dolomite limestone. Near the middle of it, a near right angle chunk had been blasted out, exposing the the bedding plane.

It was a pity we didn’t have more time here, as I’d liked to have sketched and looked at the rocks in more detail, but time was getting on and we still had more rocks to see by the Severn this afternoon. 

Sketch at Shakemantle Quarry

Links 

Open University Geological Society homepage

http://ougs.org/index.php?branchcode=ouc

Wessex branch

http://ougs.org/index.php?branchcode=wsx

1.Alan Holiday, The Severn Bore, Soudley, Beachley Point and Sedbury Cliff, Open University Geological Society Wessex Branch field trip handout (2013).

Shakemantle Quarry

Miner rescue tree sculpture