There is a lot of Portland Stone in London, so much of it in fact that I almost blank it out. I am trying to change the way I think about it, partly thanks to Gill Hackman’s inspiring book “Stone to build London” and also, whilst working on the London Pavement Geology project, to give this most iconic of London’s buildings stones its rightful coverage.
London is a good place to see all the varieties of Portland Stone quarried today and in the past, and a variety of facies and fossils can be seen in many buildings (see Siddall & Hackman, 2015; Siddall 2015, Hackman 2014). Notable examples are Green Park Underground Station and BBC Broadcasting House. However the bulk of Portland Stone Buildings in London are of fairly standard Whitbed, with little variation in facies and fossils. Typically these are white to pale-grey weathering, oolitic limestones, sometimes showing cross-bedding and with variable fossil content, mainly shells, shell fragments and occassionally pieces of Solenopora algae. The stone used at St Margaret’s Westminster is, on the whole, fairly characteristic of this description.
Easily overlooked, dwarfed as it is by its next door neighbour, Westminster Abbey, St Margaret’s Westminster is a neat little church clad in Portland Stone Whitbed. Dedicated to Saint Margaret of Antioch, it is the parish church of the House of Commons. There has been a church on this site since the 12th Century. The current building including its Portland Stone cladding dates from the 1730s refurbishment by the architect John James (1673-1746). St Margaret of Antioch was swallowed by a dragon, but was coughed up alive after she had tickled the dragon’s rib cage from the inside with her cross.
In the passage between St Margaret’s and the Abbey, towards the SE corner of the church, a block sits just above eye-level, containing a pen-shaped, brown clast, truncated by the lower edge of the block, but strikingly different from the standard allochems of the Portland Limestone. The preserved piece is around 15 cm long and 3 cm wide and has been eroded into a flattened pebble (below).
My knowledge of vertebrate palaeontology is scant and more influenced by Ray Harryhausen than anything I learned when an undergraduate. But I guessed this looked more ‘bone’ than ‘stone’. However, I have never before seen bone in Portland Stone. In the Purbeck Beds it is relatively common, but usually preserved as jet black phosphate. Thanks to the fantastic research tool that is social media, I contacted geologist Mark Godden of Portland quarry firm Albion Stone. Mark agreed that this worn pebble of brown stuff was ‘probably’ bone, as these occasionally turn up when quarrying and Mark sent some pictures for comperanda. Certainly confirmed bone from Portland Stone, recognisable as vertebra etc are a similar colour and texture. Other options where that it is an infilled burrow; however, if so, what is it that has infilled it? There is extensive bioturbation in Portland Stone, but it is all infilled with white oolitic limestone or shell fragments. So I am fairly convinced that it is a fragment of a disarticulated, much eroded and fairly large vertebrate skeleton.
According to Delair & Wimbledon (1993), the bones from several vertebrates have been found in the Portland Limestone member and equivalent strata of Tithonian (Upper Jurassic) age; crocodile and turtle bones, as well as those of marine reptiles Ichthyosaurs and Pleiosaurs are not unexpected, but dinosaur bones also occur. These may have been derived from paddling saurischians who subsequently keeled over, or more likely, were washed in from adjacent dry land, where dinosaurs such as Megalosaurus and Iguanodon were knocking around.
Reconstructions of these types animals can be seen at Crystal Palace. These Victorian effigies somewhat dated (to say the least) and are not exactly Jurassic Park. The real things are now interpreted to be the sleeker, more streamlined beasts with which the average film goer is more familiar. Nevertheless, you get the idea!
Above, left: Crocodiles and Right: Iguanodons at Crystal Palace. Below, a Megalosaurus surveys the scene.
Other notable bones to be found in St Margaret’s include those of William Caxton, England’s first printer of books, Sir Walter Raleigh and poet John Milton.
St Margaret’s Westminster is listed here on London Pavement Geology.
Many thanks to Mark Godden of Albion Stone.
References & Further Reading
Crystal Palace Dinosaurs: http://cpdinosaurs.org/visitthedinosaurs
Delair, J. B. & Wimbledon, W. A., 1993, Reptilia from the Portland Stone (Upper Jurassic) of England: A preliminary survey of the material and literature., Modern Geology, 18, 331-348.
Dino Directory: Megalosaurus: http://www.nhm.ac.uk/nature-online/life/dinosaurs-other-extinct-creatures/dino-directory/megalosaurus.html
Dino Directory: Iguanodon: http://www.nhm.ac.uk/nature-online/life/dinosaurs-other-extinct-creatures/dino-directory/iguanodon.html
Godden, M., 2012, Portland’s quarries and its stones. http://www.dorsetgeologistsassociation.com/Portland-Stone/Portland_Stone_Document_-_7_June_12.pdf
Hackman, G., 2014, Stone to build London: Portland’s legacy., Folly Books Ltd., Monkton Farleigh., 311 pp.
London Pavement Geology: http://londonpavementgeology.co.uk
Siddall, R., & Hackman, G., 2015, The White Cliffs of St James’s: Portland Stone in London’s Architecture., Urban Geology in London No. 31, http://www.ucl.ac.uk/~ucfbrxs/Homepage/walks/PortlandStJames.pdf
Siddall, R, 2015, An Urban Geologist’s Guide to the Fossils of the Portland Stone., Urban Geology in London No. 30, http://www.ucl.ac.uk/~ucfbrxs/Homepage/walks/PortlandFossils.pdf
St Margaret’s Westminster: https://en.wikipedia.org/wiki/St_Margaret’s,_Westminster