Blue Lias

Blue Lias is a sequence of layers of limestones and shales, laid down in Jurassic times, between 195 and 200 million years ago. In geology, it corresponds with the Hettangian stage of the Jurassic. It is the lowest of the three divisions of the Lower Jurassic period and, as such, is also given the name "Lower Lias". It is a prevalent feature of the cliffs around Lyme Regis and Charmouth, on the Jurassic Coast in Dorset, where it exists in layers of limestone interspersed with softer clay. It is also present in Somerset, particularly around the Polden Hills and Glastonbury, and it forms a broad plain across the East Midlands.

Blue Lias was used wherever it occurs as a building stone, and as a source of lime for making lime mortar. Because it is argillaceous, the lime is hydraulic. Since the mid-nineteenth century, it has been used as a raw material for cement, in South Wales, Somerset, Warwickshire and Leicestershire. The cement plant quarry at Rugby, Warwickshire is probably the best exposure of the formation: more than 100 layers can be seen. It also appears near Whitby in Yorkshire and Southam in Warwickshire where a pub is named after it.

Occurences of Blue Lias can be found in buildings local to its source as well as the local churches and cemeteries (where it is used in tombstones). A prime example of a 'Blue Lias' town would be Street, near Glastonbury. Other local examples of Blue lias buildings can be found in the nearby towns of Somerton & Ilchester.

It is still popular in more modern-day surroundings where it is still used in the construction of new housing developments and extensions for existing buildings in conservation areas. Blue lias is mainly used in flooring, walling and paving slabs - both coursed and layered. It is evident too in the making of flagstones and cobbles.

There are only three quarries in the country quarrying Blue Lias at present. Ham & Doulting Stone Co Ltd operate one of these, Tout Quarry near Somerton.

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The rock is rich in fossil remains from the Jurassic era. The blue-grey colour is provided by its iron content, such as pyrites.

ee also

* List of dinosaur-bearing rock formations

External links

* [http://www.nationaltrust.org.uk/main/w-global/w-localtoyou/w-wessex/w-wessex-countryside/w-wessex-countryside-jurassic_coast-walks.htm "Explore the Jurassic Coast" at the National Trust]
* [http://www.lymeregismuseum.co.uk/ The Philpot Museum website]
* [http://www.dinocoast.org.uk/ Geology of Whitby]
* [http://www.lymeregis.ukfossils.co.uk/ Geology of Lyme Regis]
* [http://www.hamanddoultingstone.com/ Ham & Doulting Stone Co Ltd]
* [http://www.soton.ac.uk/~imw/lyme.htm Geology of Lyme Regis Area]
* [http://www.soton.ac.uk/~imw/ Geology of the Wessex Coast]