A City Paleogeological Pub Crawl

In my series of posts on the rocks and stuff that make up the London Basin and the surrounding hills, I started by saying that I wasn’t interested in the rocks that were laid down before the Cotswold limestones, simply because you couldn’t see any. 

That was a lie. You can in fact see them quite easily, just not in ‘the wild’. So now I am giving you an excuse for a short pub crawl in the City of London.  OK, I know this is a thin, thin excuse for a pub crawl and it won't attract your friends but there are worse ways to indulge geomasochism. 

Many of London’s pubs were built in Victorian times and many were clad in stone that goes back a lot further in time than the sedimentary rocks that South East England is built on. Often, they are granites sourced from Scandinavia, Scotland or Cornwall.  Using stone for building became more economical once the railways offered a means of transporting it. 

If you want a massive over-generalisation, the granite from Scottish is often brown or even red; Cornish is grey and the varieties with a blue or green tinge are frequently Scandinavian. There are some rarer beasts as well. I’m not going to run through all of the different flavours of granite here. There are lots and the labels don’t tell you much.  Typical examples are shown in the graphic below.

It isn’t all granite though! Marble was also used, often inside, and usually imported from overseas, mainly Italy. There are others, such as odd sandstones and Alabaster. 

Most of these stones were formed around 200m – 300m years ago. That is, before the Jurassic era which gave us the Cotswolds Limestone. They are the legacy of a period when the map of the Earth looked nothing like it does today. Massive early continents and wide oceans formed and  disintegrated, mostly in the Southern hemisphere, with ruptures and collisions marked by violent tectonic activity. Volcanoes and mountains rose, old land masses were buried beneath new.  The magma that is released from within the Earth’s crust cools and crystallizes into quartz-rich stones such as Granite. (Marble is created a similar way but from sedimentary limestone rather than volcanic older rocks).   

The names of those continents and oceans are rather magical, to my mind at least. Gondwana and Pangaea were surrounded by the Panthalassa and Iapetus Oceans and later the Tethys Sea. The opening and closing of the Iapetus plays a big part in all this. 

The World in the 'Late Permian' period. 

Granite is practical. Rain, wind and the noxious City air doesn’t bother it much. Once polished, vomit and piss can be easily washed off. It is easily spotted, having a grainy structure and containing lots of crystals, mainly quartz, which can give it a sparkle and become very obvious once the stone is polished.  Differences in their origin and crystal content mean they come in a range of attractive designs and colours, Google ‘Granite Kitchen Worktops’ and you will see what I mean. 

Scottish granite has its origins in the tectonic chaos when the Iapetus Ocean was crushed between Gondwana and smaller continent called Laurentia. Most of the stuff you see will come from around Peterhead, north of Aberdeen. You can see it at the Bunch of Grapes at 14 Lime Street and The Walrus & the Carpenter at 45 Monument Street

The Walrus and the Carpenter

Cornwall is virtually made of granite, and theirs is the most common variety across London as a whole. It was created when Gondwana was mashed into yet another ancient continent to form Pangaea together with a swathe of mountain ranges. The Embankment and several of the bridges are made of it. But it isn’t used as much by the pubs, perhaps because its often rather dull grey colour didn’t stand comparison with the warmer tints of the Scottish stuff. You can see it outside the weird and wonderful Black Friar pub on the north end of Blackfriars’ Bridge.

Outside the Black Friars

Inside the ornate interior, the green marble is Scandinavian, the stripy green is Italian Cipollino and some of the white marble figures around the fireplace are Greek. Some of the white stone is Alabaster, which is soft like chalk and easy to carve. It forms from gypsum left in the bottom of ponds and lakes after the water evaporates. Most of it comes from the Midlands and dates back some 250m years so, again, they pre-date the creation of the limestone of the Cotswolds and the chalk of the Downs and Chilterns. A lot of lakes have come and gone since then!   

Inside the Black Friars

 Coming out of the Black Friar, notice the dark pink columns propping up the road bridge. They are made of granite from the Hebrides.  

While Alabaster is usually white and sometimes transparent, it can come in many colours and you can see a lot more Alabaster used for interior cladding in the rather beautiful ‘Counting House’ pub on Cornhill. There is a lot of other colourful stones used in this pub, but I have no idea what they are.

Just around the corner in St Michael’s Alley, is the the Jamaica Wine House, which was built on the site of a 17th Century coffee house. This is built from Red Mansfield Stone and red brick. The latter gets its colour from a high iron content and is even older than the Granites. The interior is worth a look while you are drinking your pint as well.

Jamaica Wine House

Lastly, the oldest stuff of all is probably the most difficult to see, because it is on the roof. The slate from North West Wales has been used in building since Roman times at the very least. It is over 500m years old and created when layers of ordinary mudstone morphed under immense compression as it sank and rose. This was the time when the earliest life such as Trilobites began to appear on Earth, much of which was covered in water and with an unbreathable atmosphere. What land there was would have been very hot and dry with no plant life. If you compare it with granite, you can see how much more finely grained it is.  

Granite is ubiquitous in London, being used in paving setts etc, but to my untrained eye a lot of it is just grey and featureless and, if locally sourced, comes from the same time periods as the more decorative stuff I have pointed to. Every so often you can find something a good deal older still. If you are touring the city pubs, notice the stone at the base of the walls of the  nondescript office building at 31 Gresham Street. It still isn't pretty and haven't got a clue where it comes from but understand that it is over 550m years old, when most of the land on Earth was down around the South Pole and before England and Scotland joined together.

Old, old stuff on a boring office block

No matter. Maybe I am a bit touched in the head, but I think that it is a bit wonderous to be surrounded by stuff created that was in many ways a totally alien world and at a time before even the earliest dinosaurs. Totally different than reverentially handling a fossil in a museum! 

If you are interested in this stuff, my favourite source of information is a series of walks created by Dr Ruth Sidall from University College of London. You can find a lot more of her work here: (Link) London Pavement Geology

The British Geological Society also do some very user friendly guides to what you can find in favourite  tourist spots in London,  They are here (Link) BGS Guides