Geology of Shropshire

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The geology of the county of Shropshire, England^{[note 1]} is very diverse with a large number of periods being represented at outcrop. The bedrock consists principally of ^[1] sedimentary rocks of Palaeozoic and Mesozoic age, surrounding restricted areas of Precambrian metasedimentary and metavolcanic rocks. The county hosts in its Quaternary deposits and landforms, a significant record of recent glaciation. The exploitation of the Coal Measures and other Carboniferous age strata in the Ironbridge area made it one of the birthplaces of the Industrial Revolution. There is also a large amount of mineral wealth in the county, including lead and baryte. Quarrying is still active, with limestone for cement manufacture and concrete aggregate, sandstone, greywacke and dolerite for road aggregate, and sand and gravel for aggregate and drainage filters. Groundwater is an equally important economic resource.

The Church Stretton Fault is a major structural feature forming a part of the Welsh Borderland Fault System which runs northeast from Wales, entering the county near Clun, and extending beyond the town of Newport to the southeast margin of the Cheshire Basin. The fault itself passes almost through Church Stretton, immediately east of the Long Mynd, and also passes close to The Wrekin. Another, extensive fault exists in Shropshire, the Pontesford-Linley Fault, situated near the village of Pontesbury, south west of the county town of Shrewsbury.

The oldest rocks in Shropshire are of Precambrian age and are to be found at Rushton, a mile west of The Wrekin, as schists and gneisses. East of Shrewsbury, on Haughmond Hill, the sedimentary rocks are of somewhat younger Precambrian age, and are being actively quarried for use on roads.^{[citation needed]}

The Wrekin is a prominent hill near the town of Telford. The sedimentary rock types are varied around the area, but lava and volcanic ash (tuff) from various volcanic eruptions form this famous landmark. However, The Wrekin itself is not a volcano, and never was. The primary igneous rock on the Wrekin is rhyolite; this has a pinkish colour and is usually banded as it is a slow cooling viscous extrusive rock. Intrusions of igneous rock have been quarried in the past at nearby Ercall Quarry. Here, the main type of igneous rock that can be found is granophyre. At Ercall Quarry is the contact (boundary) between Precambrian rocks and the younger fossiliferous (Cambrian) sedimentary rocks.

Much of North Shropshire is a plain which is a basin of Permian and Triassic New Red Sandstone. This basin continues north into Cheshire. Faulting has occurred within the sandstones, because of basin extension during and after the infilling of the basin. Escarpments form small prominent hills within the plain. The basin is bounded on the east by the Hodnet Fault, which runs roughly from Shrewsbury to Market Drayton. East of this fault the sandstone is thinner. In the north west of the county near Oswestry are outcrops of Carboniferous Limestone and the Coal Measures.

The Shropshire Hills AONB.^[2] were formed on a continental shelf, but buckled up into hills at the time of a continental collision: the Variscan Orogeny. The most famous of these hills is probably the Long Mynd, which is Precambrian in age and forms the west side of the Stretton Valley. East of Church Stretton is Wenlock Edge, a Silurian limestone escarpment. In between lies a complete succession through the late Precambrian, Cambrian, Ordovician and into the Silurian. South West of Church Stretton bordering Wales, is the very rural area of Clun Forest formed largely from Silurian age rocks.

Igneous intrusions outcropping at the surface in South Shropshire are few and small, but much larger bodies are believed to exist at shallow depths, evidenced by geophysical anomalies and radon-bearing groundwater.

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