Black Country Geology

The Black Country is an area located just to the west of Birmingham right at the heart of the UK. It lies between the towns of Dudley, Walsall and Wolverhampton and is noted for its industrial past. It is so named because of the thick seam of coal that runs across the region and the consequent coal mining and metalworking that developed in the area. It has no agreed borders and no two Black Country men or women will agree on where its starts or ends.

Etching of the Seven Sisters Mine, Wrens Nest

The Seven Sisters Mine, Wrens Nest (1872)

The exceptional preservation of the Carboniferous fossils found across of the region and the diversity of Silurian fossils found at the Wrens Nest, Dudley attract interest from geologists across the world.   The world’s first ever geological map, created in 1655, shows Castle Hill, Dudley and the Staffordshire Thick Coal, which at 12 metres is the thickest coal seam in the UK.  The most famous geological site of the Black Country is undoubtedly the Wrens Nest National Nature Reserve, the most fossiliferous site numerically speaking in Europe with over 700 Silurian macro fossil species and a similar number of microfossil species in a mere 50m of strata.

The geology of the Black Country is very diverse and ranges in time from the 425 – 430 million year old Silurian Period limestone hills of Dudley, through the 310 million year old muds, coals and ironstones of the Carboniferous Period and to the 250 million year old Permian and Triassic red sandstones and pebble beds, these later rocks are, in some areas of the Black Country, capped with a thin veneer of glacial deposits.

Analcime on dolerite

Analcime on dolerite from Hailstone Quarry, Rowley Regis

Over time tectonic processes (vast earth movements) have folded and broken the strata by faulting them.  This folding which forms Dudley’s limestone hills began around 490 million years ago and ended about 400 million years ago, known as the Caledonian Orogeny.  This mountain building event was caused by Baltica and Laurentia (containing present-day England and Scotland) colliding and closing the Iapetus Ocean.  Some 307 million years ago a volcanic processes deep within the Earth injected molten magma into vast sheets and chambers which now cold basaltic rocks are very hard and create the high hills of Rowley Regis.

Some of the youngest rocks found in the Black Country are the 250 million year old sandstones and conglomerate pebble-beds which were formed by flash floods in an arid, desert and later a semi arid tropical or sub-tropical environment. Most recently, repeated glaciations have scoured out the overlying rocks to reveal the present-day landscapes, with rivers now flowing through glacial melt water valleys such as the Stour Valley, such deposits can be seen at Norton Covert in Stourbridge.

A new species of annelid worm

A new species of Annelid Worn discovered at the Wrens Nest

As you read this, the Wrens Nest is still revealing exciting and new scientific discoveries.  Recently new species of microfossils have been found in samples taken from the limestone caverns beneath the town of Dudley, and carbon isotope dating has revealed new and more accurate ages for the rocks of the Wrens Nest.  International scientists from the USA are heavily involved with the Wrens Nest research and are correlating the Silurian rocks with others across the globe, changing current international timescales.

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