Open University Geological Society (London Branch)


Local Geology

Geotrails and Building Stones

Geology on the Underground

Geology on the Underground

LOUGS 21st Birthday Project

In April 2014, to celebrate 21 years of the London Branch of the Open University we launched a project which would involve all our members who use the London Underground.

London's underground stations contain a hidden building stones resource and with members across the capital there was an opportunity to collect, compile and publish information on the varieties and locations of these stones.

London was the first city in the world to construct an underground system and the project will be introduced with a description of the geology and how that determined where the original tube lines were laid. In 2014 it celebrates 150 years.

The Report is in 2 parts:
Part 1:
The Geology under London
Part 2: Stones on the Stations

Get involved!

Stage 1 - The initial stage will be information collection. If, whenever you are travelling (or changing line) on the underground, please could you note stones of interest, their location (or that there is nothing of geological interest). The easiest way is to fill in the Initial Survey Proforma and email on to: underground@lougs.org.uk. This initial data provided will form the basis of the project.

Stage 2 - If you would like to get further involved in carrying out research into the stones used in the stations and even writing them up, then there is a More Detailed Proforma to fill in. First check the list of stations which have already been submitted and again, please return to underground@lougs.org.uk.

Alternatively you can just email. We want to hear from you even if the stations you use only provide negative results.

Stage 3 - The last stage is to write up the reports to put them on the website (see Part 2: Stones on the Stations for examples).

Documents for contributors:
List of Stations checked (as of January 2015 - this is updated from time to time)
Proforma 1 survey for contributions
Proforma 2 stone details for contributions

Part 1: The Geology under London

London was the first city in the world to construct an underground system. In this section we will examine the geology under London to determine where the original tube lines were laid and subsequent problems when extending the lines into less favourable geology.

Section under construction - more to follow

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Part 2: Stones on the Stations

LOUGS students have located a number of stations on London's underground that have used natural stone in their construction or decor. These have been researched and written up by those who located them.

District & Circle Lines

St James Park - Anna Saich

Piccadilly Line

Knightsbridge, St James Park, Piccadilly Circus - Diana Clements

District & Circle Lines

St James Park

St James Park underground station includes the London Underground Headquarters at 55 Broadway. London’s first ‘skyscraper’ has the District and Circle line running beneath it. A Grade I listed building it was designed by the architect Charles Holden and was built in the late 1920s, a time when building stone was still generally sourced from Britain. 55 Broadway is of concrete and steel frame construction with an exterior cladding of Portland Stone ashlar. The stone façade showcases a number of sculptures by eminent pre-WWII artists and at ground level there are granite columns around the exterior of the building.

Historically, Portland Stone was a common building stone across London and was used extensively by Christopher Wren when rebuilding the City of London following the Great Fire in 1666 (including the new St Paul’s Cathedral). Initially quarried from coastal quarries on the Isle of Portland in Dorset and shipped to London, Portland Stone is now extracted from underground mines by Albion Stone (www.albionstone.com/portland-stone). Portland beds are pale cream to white oolitic limestones formed in the warm, shallow seas of the late Jurassic. Within the Portland succession four beds are recognised the Basebed, Curf, Whitbed and Roach with varying amounts of fossils in the different beds. Only a few fossils can be seen in the Portland Stone at St James Park.

Internally the public shopping arcades and ground floor booking hall are clad and paved with travertine, a popular choice for use in underground buildings of the period. Like the Portland Stone, Travertine is a limestone, but it is formed in a very different way to the Portland Stone. This banded freshwater limestone is deposited at geothermal springs. Calcium carbonate rich water emerges at the surface and as the pressure drops the calcium carbonate precipitates out.

The Portland Stone exterior
The travertine cladding to the shopping arcade and booking hall

Piccadilly Line


The beautiful creamy limestone cladding the walls of the platforms, ticket area and access tunnels at Knightsbridge station is partly behind the inspiration to describe the Stones on the stations on the London Underground. Nowhere else has such an extensive use of natural stone been located.

This highly polished limestone is known as a ‘marble’ in the trade. However, it is not a true marble as fossils can clearly be seen. Marbles are strictly metamorphosed limestones formed during mountain building processes of high heat and/or pressure where the original material is transformed obliterating the shape of any fossils that formerly existed. This stone has become sufficiently hardened over the last 150 million years to take a good polish.

The fossils in this stone are very distinctive. There are ammonites, coiled relations of octopus, squid and cuttlefish with distinctive hard shells. They became extinct 65 million years ago along with the dinosaurs. The ammonites in this stone are not usually very well preserved as the shells were aragonite which decays with time. Nevertheless their coiled nature is easily identified. Another extinct relative is the belemnite and this rock is instantly identifiable by the good preservation of the brown internal guards of these animals. Unlike the ammonite the hard parts are calcite which is much more durable. The fossils look something like bullets and indeed they were thought to be thunderbolts before the nature of fossils as the remains of ancient animals was understood. The guards can be compared to the white internal hard parts of cuttlefish, a source of calcium for caged birds and often seen in cages of parrots. Another characteristic of this stone is the rather amorphous brown structures. These are remains of sponges and the white flecks are rather enigmatic microfossils. Remains of bivalves can also be found.

The association of the fossils, and particularly the belemnites help to identify this stone as a Late Jurassic limestone (c. 150 Million years old) from Bavaria, in southern Germany, part of the sequence that also produced the exceptional preservation of the slightly younger Solnhofen fauna, famous for the earliest known bird, Archaeopterix. This rock, known as Treuchtlingen ‘Marble’ does not preserve the soft parts of the animals. Treuchtlingen Marble has become fashionable in London during the last decade or so and can be seen in the new Cannon Street station development as well as on the floor of Westfield Shopping Centre in Stratford.

Access tunnel cladding

Belemnites showing details of phragmocone
Belemnites showing details of structure

Piccadilly Line

Green Park

Whilst the platforms and ticket offices of Green Park Underground station are clad in ceramic tiles, the station is included for its magnificent south entrance created in 2011 as an artwork by sculptor John Maine His Sea Strata is featured on the TFL website Art on the Underground where you can read about the inspirations behind the creation. Both John Maine and TFL should be congratulated. Let’s have more please!

The idea of creating a gazetteer of Geology on the Underground sprang from Sea Strata. It is aptly named as it features different layers (or strata) of the Portland Limestone which is quarried on the Isle of Portland and has supplied London with stone for many of its important monuments dating from the time of the Christopher Wren churches rebuilt after the Great Fire of 1666 to the present day. In the early days it was loaded directly onto ships and brought to London by sea, now it mostly arrives by road from underground mines.

This monument to Portland Stone features the ‘inferior’ Portland Roach in all its glory. Panels on the lower half are cladding of the fossiliferous Portland Roach where only the external mould of the exterior of the fossils remain, leaving holes where the shells had been. At the top are panels of the much-prized Basebed or ‘Best Bed’ of Portland freestone, where John Maine has carved larger versions of the holes left by the decayed fossils. In particular he features the Portland Screw (the gastropod Aptyxiella portlandica). The intervening layers are formed of the ubiquitous Whitbed with varying amounts of thick Oyster shells preserved within the stone. The stone comes from Albion Stone quarries on the Isle of Portland and their website provides more details: www.albionstone.com (including a "stones overview" (see section pictured) and the specifications of the various stones used); details of the stone supplied for Green Park Underground station are described at: www.albionstone.com/portfolio_item_green_park_tube.html.

To complete the artwork John Maine has added paving of cubes of 3 different varieties, one red, one dark grey and another, paler grey. Each cube has a spiral carved into it reminiscent of ammonites that can be found in the Portland strata although no ammonites have been identified within the artwork itself.

John Maine Sculpture Green Park.JPG
Portland Stone quarry.jpg

Piccadilly Line

Piccadilly Circus

Piccadilly Station was opened in 1906 and rebuilt beneath the streets in 1928. The ticket area and access passageways to the street are extensively clad in a rock-type fashionable at the time, the limestone travertine. Unlike most limestones that are laid down in seas or even freshwater lakes, travertine is precipitated from calcium-carbonate rich springs, often associated with spas. When rainwater falls on limestone rocks the small amount of acid within it slowly dissolves the limestone. This is how caves and natural sinkholes are formed. The water re-emerging at the surface is saturated with calcium-carbonate that is then precipated, often forming spectacular displays as at Pamukkale in Turkey. Only small localised outcrops of travertine are found in the UK and most of the material used for building traditionally comes from Tivoli near Rome. It is only 50,000 years old, much younger than most of the rocks used in the building of London which are mostly hundreds of million years old. The travertine formed at Tivoli comes from a geothermal area heated by local volcanic activity. One of the common features is the delicate shrub-like forms which are composed of fine aggregates replacing the original cyanobacteria build ups. Tivoli is probably the source of the travertine in Piccadilly Circus.

The stone has not fared well in the station. As the rock is formed it envelops organic material such as bacterial mats, reeds and grass which then decays leaving holes. Over the years these holes have become filled with London grime. Sometimes these holes are ‘stopped’ with a resin so that they retain their original appearance, particularly when used exteriorily. It is a pity that did not happen at Piccadilly.

At the top of the exit steps to the street is a trim of grey granite of unknown provenance.

Travertine formation in the walls of the ticket area at Piccadilly Circus

Pamukalle, Turkey
Grey granite trim at street level

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