Monday, 29 May 2023

The 'Geological Illustrations'

The Coal Measures cliff

As a geologist, the highlight of my trip to Crystal Palace Park in April 2021 was undoubtedly the ‘dinosaurs’ – a set of palaeontological reconstructions by Benjamin Waterhouse Hawkins – but these were just part of a much bigger project devised by Joseph Paxton and the consultant geologist David Thomas Ansted, with their construction by James Campbell, which were originally known as the 'Geological Illustrations'.
To provide an appropriate setting for the animal sculptures, the landscaping was designed to represent the geology of Britain from the Primary (Precambrian-Lower Palaeozoic), to the Secondary (Upper Palaeozoic-Upper Cretaceous) and Tertiary (Cenozoic–Quaternary) eras, with rocks matching the age of the animals being brought in from appropriate sources or, in the case of the plinth of the Megaloceros, constructed using Thames Gravel. 
Megaloceros standing on a plinth made with Thames Gravel

Walking along the path from the Tertiary Island to the Secondary Island, I have to say that I was too busy trying to take a good photograph of the Megalosaurus and I only noticed the small cliff of Portland limestone in the background, when reviewing my high resolution images for this Language of Stone Blog a year later. 
A small cliff of Portland limestone behind Megalosaurus

Due to their obscured location, I had missed entirely the Chalk upon which the Pterosaurs have been placed but, arriving at the Paxton Bridge, large quantities of the Upper Carboniferous Rough Rock sandstone has been used to form a ‘riverbed’ and various extensive reproduced rock exposures that look quite authentic. 
Landscaping with Rough Rock

From the early 1840s onwards, geology was included in formally laid out urban parks as a feature of urban planning and Joseph Paxton had already demonstrated his ability to create large landscaping features at Chatsworth House - the Rock Garden and the Strid. The large blocks of Rough Rock were quarried from Bramhope in West Yorkshire, which would have been expensive, but the artificial stone Pulhamite was used for many large landscaping projects from this time onwards, at a much reduced cost.
A view of the Coal Measures cliff

Continuing along the path, I was very surprised to encounter the Coal Measures clff - a complex feature that includes a horst and associated faults - which has coal cut in blocks and accurately relates to the sandstones and ironstones that are typical of the Clay Cross colliery from which the materials were obtained.
The Coal Measures cliff

The idea of this part was to illustrate the natural resources that had enabled the industrial revolution to take place. Apparently, at least one of the directors of the Crystal Palace Company was also the director of the Clay Cross colliery in Derbyshire, including the mining engineer James Campbell, who was responsible for the construction of the original cliff of Mountain Limestone (Carboniferous Limestone). 
The Mountain Limestone cliff

From the opposite side of the path, although I needed the zoom lens on my camera to see them, the four footed Iguanodon is standing on a plinth that is built with Wealden sandstone and a small ‘cliff’ of Jurassic oolitic limestone from the Cotswolds is set on the edge of the Secondary Island, behind a Teleosaurus.
Jurassic oolitic limestone behind a Teleosaurus

Further along the path, the gated and inaccessible entrance to a three-quarters scale lead mine can be seen in the Mountain Limestone. The feature, which included pipe veins, rake veins, and stalactites, was completely destroyed in the 1960s during remodelling of the waterfall; however, enough remained to be able to carry out archaeological investigations and subsequent rebuilding (2001-2003) using 110 tonnes of Carboniferous Limestone that was obtained from Once-a-Week quarry, near to the original source in Derbyshire. 
The entrance to the reconstructed lead mine

The original feature was constructed with Devonian Old Red Sandstone beneath the Carboniferous rocks, with Triassic New Red Sandstone above, but the feature is only visible from a distance and I could not see any evidence of these. 
Information on the Coal Measures cliff

As with the ‘dinosaurs’, a well designed information panel is strategically placed on the path, which describes the rocks that are represented and provides the visitor with an introduction to geological time, stratigraphy and the means of dating rocks. 
Information on geological time

Making my further along the path beyond the Ichthyosaurs and Plesiosaurs, I could quite clearly see another curved cliff made of White Lias limestone but I saw no signs of the Triassic red sandstone that has been used in the landscaping in the area where the Labyrinthodons and Dicynodons have been placed.
A cliff of White Lias limestone

Sunday, 21 May 2023

The Crystal Palace Park Dinosaurs

 A detail of an Iguanodon

Continuing my investigation of Crystal Palace Park, having made observations on its geology and the building stones used for the terraces, I arrived at the north-east end of the Lower Lake, where an information panel provides an introduction to the Grade I Listed Geological Court – an internationally important collection of palaeontological sculptures that were made by Benjamin Waterhouse Hawkins between 1852 and 1854, with advice by Sir Richard Owen. 
An interpretation panel

A quick search on Google shows that these unique representations of vertebrates, from the late Permian to the Quaternary periods, have been studied in great depth over the years. Relying mainly on the Friends of Crystal Palace Park Dinosaurs website for my information, here are a just a selection of photos from and hour and a half spent wandering around the Geological Court.
Megaloceros with a broken horn.

My first view was of Megaloceros, or the Irish Elk, which I had first encountered at the Sedgwick Museum in Cambridge, during my free time on a field trip with the Heart of England language school, and I was saddened to see that one of its horns was broken - just one of the problems for the conservation of this unique educational resource.
A Megaloceros family

Various artificial strata have been laid out on the various islands, to represent the geological age of the sculptures that are set upon them. Although I didn’t notice it at the time, I have since become aware that the plinth to one of these is made from Pleistocene to Holocene Thames gravel. 
Palaeotherium and Anoplotherium
Moving on to Tertiary Island, I encountered Palaeotherium and Anoplotherium, which lived in the Eocene period. When growing up in London and visiting both the Natural History Museum and the Geology Museum very often, I was very interested in the various fossils on display, but I had never heard of these mammals before. 

From a distance, I could get a view of the Mosasaurus at the water’s edge, which lived 70 to 66 million years ago at the end of the Cretaceous period, is the only deliberately incomplete restoration in the entire Geological Court, comprising just a head and neck and with a single flipper. This is sometimes attributed to its sculptor not having enough anatomical information, as the skull was the only fossil material available at the time. 
A detail of Mosasaurus

Although the sculptures made the most of the scientific information available at the time, many of the anatomical reconstructions are now considered to be very inaccurate, with the depictions of the Iguanodons receiving much attention – particularly the bone that was once considered to be a horn on the nose, but which later discoveries suggest it to be a thumb spike. 
The four footed Iguanodon

The two models of Iguanodon also reflect conflicting ideas in the 1850’s about its stance, with one being firmly four footed like an elephant, with another representation showing it sprawling on a tree trunk like an iguana. Later fossil finds had shown that these had well developed powerful hind limbs and less well developed forelimbs but, according to the Natural History Museum, it is considered that Iguanadon was predominantly a quadruped.
The sprawling Iguanodon

I could only see the rear of the early Cretaceous Hylaeosaurus, with its spiny back, from a distance. Along with Iguanodon and Megalosaurus, it is one of only the three genera at Crystal Palace Park that would be actualy be classified as a dinosaur. It was also the first armoured ankylosaur known and was discovered by Gideon Mantell, who is probably best known for his work with Iguanadon bones and teeth.

The mid Jurassic Megalosaurus, which features in the opening lines of Bleak House by Charles Dickens, is again now considered to have been a bipedal dinosaur with shortened forearms and the humped shoulders discounted, on the basis of subsequent fossil finds. 

I could only get a view of the head and neck of one of the two remaining Pterosaurs at a distance, with my zoom lens, but it was partly obscured by vegetation and I didn't get a very good impression of it. These ‘winged lizards’ existed from 228 – 66 million years ago, with the Pterodactylus cuvieri on display being from the late Cretaceous period. 

A Pteranosaur

There is a much better view of the marine reptiles, which are the sculptures at the Geological Court that I am most familiar with, having seen many specimens at the Natural History Museum as a child and later after I had qualified and worked as a geologist.

The three species of early Jurassic Ichthyosaurs are based on the discoveries by Mary Anning at Lyme Regis in the early C19, which are also on display at the Natural History Museum, but I don’t recount seeing the crocodile like Teleosaurus before. 
A Teleosaurus

Continuing with my observations of the sculptures on Secondary Island, the models of the three early Jurassic species of Plesiosaurs are depicted as having long snake like necks, but modern studies of anatomy suggest that were not flexible enough to form tight curves. 
A detail of a Plesiosaur

Moving on along the path, I next encountered three sculptures that depict different species of the Triassic Labyrinthodon, which are thought to have been primitive amphibians. They were portrayed as giant frog-like creatures, with a mix of smooth and warty skin, but modern thinking considers them to be more like salamanders and they had a well developed tail. 

Next to the Labyrinthodon sculptures, there are two examples of the late Permian Dicynodon whose fossil remains have been interpreted by palaeontologists as ‘mammal like reptiles’. Most fossils at the time of the reconstruction were heads, which showed the tusks and the horny beak, but the turtle like body was conjectural.

I took a very quick diversion to take a look at what I thought was a large stone sculpture, set higher up on what appears to be a natural gravel terrace, which children were playing on. According to the website, this is the original head of the Hylaeosaurus and that the one on the in situ dinosaur is a glass fibre replica.
The original head of the Hylaeosaurus

Walking around the south side of the Lower Lake, I finished my brief exploration of the Geological Court by photographing the Megatherium, which is also known as the giant ground sloth. I had got glimpses of the back of its head earlier on my walk through the Geological Court, but this giant creature, which is the one sculpture made from solid limestone, was meant to be seen from this vantage point.

Thursday, 18 May 2023

The Terraces in Crystal Palace Park

Sphinxes in Crystal Palace Park

My very brief investigation of Crystal Palace Park started at the north-west entrance, from which I made my way down to the Grade II Listed Italian Terraces, which are all that are left of the Crystal Palace – after it was burned down in 1936 and the water towers later demolished. 
A sphinx on a plinth made of grey granite from south--west England

Although I grew up in South London, I had only visited Crystal Palace Park a couple of times before – to see the dinosaurs – and the recently restored artificial stone sphinxes took me by surprise, with their brick red coloured paint. 
A headless statue

The sphinxes are set on grey granite plinths at each side of a wide set of steps, which are built of the same granite, but I didn’t stop to closely examine it here and was more interested in the limestone that is used of the balustrades to the upper terrace and a headless statue – one of three that remain from the original row of statues that represented the different parts of the empire.
The balustrade to the upper terrace

With the balustrade being fenced off, I couldn’t get close enough to examine the limestone with my hand lens but, from the cream colour that I could see beneath the grey patina, I could tell that it is a Jurassic oolitic limestone – probably from the area around Bath.
A view from the upper terrace

I continued along the upper terrace until I reached the central flight of steps, where I could not help but notice the rectangular feldspar phenocrysts in the granite, which are characteristic of those quarried from the Cornubian batholith in Cornwall and Devon. 
White feldspar phenocrysts in the granite paving

Although familiar with their general physical characteristics, the granites from this region very considerably in colour, mineralogy and texture and I couldn’t say where the stone came from. In some places, the white feldspar phenocrysts are greater than 50 mm in length, which I had not encountered before. 
Large feldspar phenocrysts
Finding a place where the ground beneath the upper terrace was not fenced off, I went to have a closer look at the oolitic limestone, which here does not have such a well developed grey patina as that seen on the balustrade. 
A view along the upper terrace

Looking closely, with out using a hand lens, the limestone appears quite coarse grained, with shelly beds and graded bedding being differentially weathered, which highlights the well developed cross-bedding in the limestone. 
A detail of limestone walling with shell beds and cross-bedding

In one place, a section of the stone facing to the brick built core of the terrace walling had failed and, while awaiting repair, had a barrier place around it but I managed to obtain a sample of limestone from a small pile of rubble. It contains no shell and, when looking through a hand lens, the ooliths are very clearly visible along with the calcite that cements them together. 
A sample of oolitic limestone

Continuing along the wide granite paved walkway to the lower terrace, I stopped again to look at further examples of very large feldspar phenocrysts, which did not have a very well defined rectangular shape.
A very large feldspar phenocryst

I didn’t explore the masonry to the arched lower terrace and just took a few general record photos of the principal features on either side of the central flight of steps and took another look at the gravel on the unpaved part of the lower terrace, which is mainly composed of black flint pebbles. 
A general view of the lower terrace

Leaving the terraces behind me, I then made my way down towards Main Centre Walk and unexpectedly came across the large Grade II Listed bust (1869) of Sir Joseph Paxton, which is signed by the sculptor W. F. Woodington and is described in the Historic England listing as being Carrara marble.
The bust of Sir Joseph Paxton

Monday, 15 May 2023

Geology at Crystal Palace Park

A broken flint pebble from Crystal Palace Park

Following on from my investigation of the geology and historic architecture in and around Wadsley Park Village, my next trips coincided with a week spent in London – to help my 92 year old mum after she had come out of hospital, having fallen over and broken her hip when scarifying the lawn. 
Crystal Palace Park
Having completed essential tasks such as mowing the lawn, watering various plants, clearing up fallen blossoms, moving potential trip hazards and doing the shopping - while at the same time photographing various listed buildings around West Wickham for the British Listed Buildings website – I set out to explore Crystal Palace Park, with the intention of visiting its ‘dinosaurs’. 
The 1921 geological memoir for South London describes the Crystal Palace ridge, along with isolated plateaux of Richmond Park and Wimbledon Common, as being amongst the principal topographic features. Standing at a height of 110 metres above sea level, this high point is now emphasised by the Crystal Palace transmitter, which can be seen from miles around. 
This high ground in the Tertiary strata is formed by the Claygate Member, the sandy upper part of the London Clay Formation, which differs considerably from the lower part - a heavy, blue/grey homogenous clay that I remember from digging trenches for foundations in north London, when working as a builder’s labourer before studying geology at Nottingham University. 
A topographic map of the Crystal Palace ridge

Growing up in South London, I clearly recall the topography formed by the various river terraces that drop down from Clapham Common and the steep slope that rises up to Upper Norwood but, apart from my brief exploration of Wimbledon Common the year before, I had never given much consideration to London’s geology. 
A walkway cover in flint pebbles

Having had a quick look at the various terraces, which are the remains of the Crystal Palace that burned down in 1936 and will be described later, I was very interested to discover that the various walkways are covered in gravel that is composed largely of various sized pebbles of black flint. 
The geology around Crystal Palace Park

I later learned that the highest part of the Crystal Palace ridge is covered by Quaternary gravel of an unknown age which, according to the geological memoir, consists mainly of Chalk flints, with a large proportion of Tertiary pebbles and Greensand chert, which are derived from the south and probably represent the outwash from snow or ice covered ground that was beyond the limits of the Pleistocene ice sheet. 
Flint pebbles from Crystal Palace Park (21 mm diameter coin)

Having picked up a few pebbles to add  to my rock collection, I then made my way down to the Information Centre, where I came across a large boulder of Precambrian Lewisian gneiss – one of the ‘Millennium Rocks’ from the coastal village of Lochinver in north-west Scotland, which were given to the borough of Bromley in 2000. 
A boulder of Lewisian gneiss
Although this rock is obviously not an example of the local geology, every student of geology in the UK is taught about the Lewisian gneiss in the north-west of Scotland – which very few will ever visit – and it was therefore a very pleasant surprise to discover this.
A detail of the Lewisian gneiss