Saltwells National Nature reserve contains 2 sites of Special Scientific Interest (SSSIs) for its geology and a protected ancient site of bellpits and ancient coal working.

The site shows two distinctly different periods of earth history, when very different conditions were present. The first and oldest rocks contain evidence of the change from ancient seabed to dry land. The second series of layers show how this land was covered by huge swampy forests with trees growing up to 45m in height that created the coal seams.

The structure is a broad upfold or anticline with rocks dipping to the West and East offset by several faults.

The Tramway exposures and Brewin’s Bridge canal section (SSSI)

This cutting is all that remains of an old inclined tramway which was used to carry minerals from Doulton’s Claypit up to the Dudley No.2 Canal located further up the slope. The rocks along the tramway are sedimentary rocks. Pale grey to green layered, shales, mudstones and fine grained sandstones. Some layers contain the fossil remains of sea creatures. The layered sequence gradually becomes more sandy towards the top. The rocks are of Silurian age dating between 420 and 417 million years ago. During this time an ancient shallow, tropical sea bed was squeezed by earth movements and slowly rose out of the waters to become dry land.

In stark contrast, close to the canal, the rocks change to a dark dense and hard igneous rock called microgabbro, similar to basalt. Huge earth movements faulted the Silurian rocks allowing molten magma to force it’s way in forming irregular shaped intrusions, cooling to form the microgabbro 307 Million years ago.

The microgabbro can be seen along the canal then, along a faulted contact, the pale green sedimentary rocks of the Silurian reappear. They can be traced along to the Brewin’s Bridge canal section. Then a marked change takes place. The fine grained sands and shales are replaced by layers of pebbly and gritty sandstones with an orange or reddish colour. The pebbles and grit indicates the rocks were deposited by fast moving rivers. The colour indicates they were above water and iron minerals were exposed to the air.  Occasional lens of coal represent flattened tree trunks carried by the rivers. These rocks are of Carboniferous age. The thin uneven boundary between the Silurian rocks and the Carboniferous grits is called an unconformity. It marks a huge 100 million year gap in time between the Silurian rocks being uplifted and Carboniferous rock being deposited.  

 

Doulton’s Claypit (SSSI)

The claypit is the result of clay extraction by the Doulton company to produce sanitaryware. It was abandoned in the 1940’s.

Doulton's claypit with spectacular cliffs shows a section through the rocks of the Lower and Middle Coal Measures (330-310Ma) part of the Carboniferous period. The rock layers formed when the area was covered by huge flooded tropical forests.

At the top of the rock face there are now trees, this is where the famous thick layers of South Staffordshire Thick Coal were once extracted. The scars of this extraction now hidden by woodland. The coal seams formed from the remains of ancient plants, tree ferns and club mosses, growing up to 45 metres high. Distinctive dark layers in the cliffs are coal seams and coal shale. The upper layer is called the Heathen coal.

The grey muddy rocks and clays are the swamps and ancient soils of those forests. The layers of coarse sandstones formed from rivers flowing through and flooding the forest. Fragments of the plants remain as coal in the sands. Layers and nodules of ironstone formed in the wet sediments.

 At the end of the Carboniferous great earth movements folded and faulted the landscape, tilting the rocks in the claypit to the East as we see them today.

 

Bellpits area (scheduled ancient monument)

This is the site of collapsed mines called bellpits. This area of the woodland is now a scheduled ancient monument due to the remains of the bellpits and other coal mining activities. Here the South Staffordshire thick coal, up to 10metres thick, was exposed. It was worked from the medieval period through to the industrial revolution.  At first it could be dug from surface trenches. The coal dipped down to the West so later bellpits were needed to reach it. As the technology of the industrial revolution improved, coal could be extracted from deep and open cast mines, the bellpits were abandoned.

 

 

 

       

 

                                 Click on the PDF to download Saltwells Geosite leaflet to explore the geology of Saltwells first hand                                           and to learn about Saltwells part in the Black Country Geopark.

​

​

If you are unable to visit the Geotrail at Salwells, take a virtual tour by clicking on the following link-

https://festivalofgeology.org.uk/saltwells/

​

With thanks to The Geologists' Association, The Black Country Geopark and Dudley Museum at the Archives.

​

 

​