Urban Geology New Year Quiz 2017

This quiz was first posted on Twitter over the New Year Weekend of 2017-2018. If you missed it, both questions and answers are given here. Scroll down for answers.

 

Q1. Where do these coloured marbles come from?

A. Tuscany, Italy

B. Derbyshire, England

C. Devon, England

D. Namur, Belgium

 

Q2. Which is the main building stone of the British Museum?

A. Bath Stone

B. Lincolnshire Limestone

C. Portland Stone

 

Q3. This well known building stone is a rapakivi granite called Baltic Brown. Where is it quarried?

A. Denmark

B. Estonia

C. Finland

D. Sweden

 

Q4. When were the Carrara Marble quarries first worked?

A. Neolithic

B. Roman Period

C. Renaissance

D. 19^th Century

 

Q5. This is a very well-known building stone called Larvikite because its found in Larvik, Norway. Noted for its iridescent feldspars, what kind of rock is it?

A. Granite

B. Syenite

C. Monzonite

D. Gabbro

 

Q6. What type of granite is this?

A. Rubislaw Granite

B. Shap Granite

C. Dartmoor Granite

D. Sardinian Granite

 

Q7. These two stones have been used on the Titanic and for St Peter’s Throne in the Vatican. In which mountain range are they quarried?

A. Atlas Mountains

B. Betics

C. Pyrenees

D. Alps

 

Q8. This fossiliferous stone is currently very fashionable, used for exterior cladding as well as paving in malls and stations. Where is it from?

A. Paris Basin

B. French Jura

C. Bavarian Jura

D.Portland Dorset

 

Q9. These two porphyries were the main stones used in a Medieval paving technique called ‘Cosmati Work’. At the time they were looted from Roman ruins, but where were they originally quarried?

A. Italy and France

B. France and Turkey

C. Turkey and Greece

D. Greece and Egypt

 

Q10. How much granite was used in the construction of London’s Victoria Embankment?

A. 500,000 m3

B. 1 million m3

C. 1.5 million m3

D. 2 million m3

 

 

Answers

Q1: Devon, England.

These colourful limestones were quarried around Torquay, Plymouth and Ashburton in Devon and were popularly used for decorative items made by the English pietra dura industry during the 19^th Century. The black limestone in which they were set is from Derbyshire.

So called ‘Devon Marbles’ were worked small-scale from the Frasnian-Givetian age Tamar Group Limestones of south Devon. You can find out more about the geology of these stones and there use in decorative works in Gordon Walkden’s books published by the Geologists’ Association.

Walkden, G., 2015, Devonshire Marbles: their geology, history and uses. Volume 1. Understanding the marbles. Geologists’ Association Guide no. 72., The Geologists’ Association, London.,1-232.

Walkden, G., 2015, Devonshire Marbles: their geology, history and uses. Volume 2. Recognising the marbles. Geologists’ Association Guide no. 72., The Geologists’ Association, London., 233-484.

 

Q2. Portland Stone.

Like many of London’s great civic buildings of the 18^th and 19^th Centuries, The British Museum is built from Upper Jurassic Portland Stone. Find out more on London Pavement Geology.

Bath Stone and Lincolnshire Limestone are also important British, Jurassic, oolitic limestones which are important building stones, however, the introduction of Portland Stone after the Great Fire of London in 1666 eclipsed their use in the capital.

 

Q3. Finland

This stone is quarried from the enormous Vyborg (Wiborg) Batholith which straddles the Finnish-Russian border. The stone shown in the photo and exported globally is quarried in Finland from several quarries near Lappeenranta in the SE of the country. It is a variety of rapakivi granite (‘rapakivi’ is a Finnish word meaning rotten rock) called a wiborgite. This rock has the distinctive ‘ovoid’ zoned feldspar megacrysts. Find out more in Axel Muller’s article in Geology Today.

Müller, A., 2007, Rocks Explained 1: Rapakivi Granites., Geology Today, 23 (3), 114-120.

 

Q4. Roman Period

Although it is probably the case that pre-Roman societies used field stones from the Massa e Carrara region for small scale use, ‘quarrying’ as we understand that term today began during the Roman period. The Romans quarried several marbles from the Carrara region including the white variety which they called ‘Luna’.

 

Q5. Monzonite

Larvikite is a monzonite, a plutonic igneous rock containing no (or very minor) quartz and equal amounts of plagioclase and K-feldspar. The iridescent (‘schillerescent’) feldspars are antiperthites with an oligoclase host and K-feldspar blebs. Find out more about the geology and use of this famous building stone here:

Heldal, T., Meyer, G. B. & Dahl, R., 2014, Global stone heritage: Larvikite, Norway., in: Pereira, D., Marker, B. R., Kramar, S., Cooper, B. J. & Schouenborg, B. E. (eds) Global Heritage Stone: Towards International Recognition of Building and Ornamental Stones. Geological Society, London, Special Publications, 407, 14 pp.

 

Q6. Dartmoor Granite

This is ‘Giant Granite’ from Dartmoor, so-called because of the large megacrysts present in this rock. There are several ‘megacrystic’ granites used in the building stone trade because they are both strong and decorative. A ‘megacryst’ is a phenocryst in a granite which is bigger than 1-2 cm. The megacrysts in Dartmoor ‘Giant Granite’ can be 10-15 cm long. Rubislaw Granite (from Aberdeen) does not contain megacrysts. Shap Granite and some varieties of Sardinian Granite are megacrystic, but usually the megacryst are on the small size. The give-away here are the lace-like blobs of black tourmaline which is characteristic of the Dartmoor Granite facies quarried around Princeton and elsewhere in the north of the pluton. The example in the photos is from Fishmongers’ Hall in London.

 

Q7. Pyrenees

A number of very decorative tectonic breccias have been quarried in the Pyrenees since the Roman period. Shown here is the pink-grey variety Sarrancolin which was used in the dining room of the Titanic (designed by Charles Fitzroy Doll who also designed the Russell Hotel, where this stone is also used). The black and white stone is generally called Grand Antique. It was first quarried by the Romans and has been worked on and off since. The quarries have recently been brought back into production by Carrieres Plo. This stone has been much favoured by the Catholic Church. It is used for the plinth of the statue of St Peter Enthroned in the Vatican and this statue (including the stones used) has been much replicated.

 

Q8. Bavarian Jura

This stone is known as ‘Jura Marble’ in the building trade. Geologically it is from the Kimmeridgian Treuchtlingen Formation and it is quarried in the Altmühltal Naturpark, Southern Frankonian Alb, Bavaria, Germany.

 

Q9. Greece and Egypt

The green porphyry is called Lapis Lacedaemonium and it was quarried near the village of Krokeai near Sparta (Spartí), Greece. This is an altered Triassic basalt. It was worked from the Bronze Age until the Byzantine Period (5^th Century AD).

The purple porphyry is the ‘original’ porphyry, named by the Romans because of its colour. It comes from the Roman Quarries of Mons Porphyrites in the Eastern Desert of Egypt which were in operation from (probably) the 3^rd Century BC to the 5^th Century AD. The rock is an andesite from the Neoproterozoic Dokhan Volcanics. It contains the epidote mineral piedmontite which is partially responsible for imparting the purple colouration.

 

Q10. 500,000 m3

Did you get lucky here? Half a million metres cubed of granite were used in embanking the Thames, the bulk of the material used was earth to backfill the new land reclaimed from the river.

Surprisingly little is written about this incredible feat of engineering. Find out more here:

Siddall, R. & Clements, D., 2015, Never in the field of urban geology have so many granites been looked at by so few! A stroll along the Victoria Embankment from Charing Cross to Westminster & Blackfriars Bridge., Urban Geology in London No. 21, 19 pp.

 

How did you do?

 >8/10 You are a building stone expert! But here’s a #toptip – don’t give up your day job!

5-8/10 Pretty good! You have some sound stone skills!

3-5/10 OK, but definitely room for improvement …

< 3/10 Better luck next time!

 

Happy New Year and thanks for participating the #UrbanGeologyQuiz!

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Christmas Geobaubles 2017

Here are my thin section Christmas geobaubles for 2017.

For festive geologically themed decorations, print off two sheets, cut out the baubles and stick the two sides together. Pierce the black hole in the tag to thread a string.

Merry Petrological Christmas Everyone!

Ruth  xxxx

 

PS Here are last years (2016) Geobaubles

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Tyndall Stone: An Iconic Canadian Building Stone

Tyndall Stone is one of Canada’s iconic building stones. Derived from near Garson, Manitoba, it is used in a great number of buildings in Winnipeg. However it shows up all over the place as a high quality and attractive stone, suitable for both exterior and interior use with honed, bush-hammered or a polished surface. With a compressive strength of 62.8 MPa, it is a very strong and durable construction limestone.

Tyndall Stone-clad portico of the Fairmont Chateau Lake Louise in Banff National Park, Alberta

Tyndall Stone is extracted from the Selkirk Formation of the Red River Group of the Williston Basin. Tyndall Stone is quarried at Gillis Quarry in south western Manitoba, but extends westwards into Saskatchewan where the lateral equivalent is known as the Yeoman Formation. These formations are overlain by evaporite deposits. Gillis Quarry exposes a 43 m thick unit of massive, metre-thick beds and have allowed excellent exposures for 3D scientific study of this stone. The rock is of Upper Ordovician (Katian, 445-453 Ma) age.

The Gillis Quarry is located around 40 km northeast of Winnipeg (see Google Maps). Most sources seem to agree that the first use of this stone was at Lower Fort Garry built in the 1830s. Gillis Quarries were brought into commercial production in 1910 and have remained in the same family ever since. The stone lends itself well to both traditional and modernist architectural styles, with finishes ranging from rough, quarry-dressed blocks to smooth, honed or polished ashlars.

Tyndall Stone is a limestone, but with a significant dolomite content.

The most striking thing about this stone – and its main decorative feature – is that it is pervasively riddled with Thalassinoides trace fossils. These are branching burrows, with T- or Y-shaped junctions made by creatures tunnelling through the soft sediment, which are typically 1 to 2.5 cm wide. These show up brown in contrast to the cream-coloured limestone matrix, this is because the burrows backfilled with dolomite. It is not known what made these burrows during the Upper Ordovician, but modern Thalassinoides burrows are made by the shrimp Callianassa so a similar crustacean is a reasonable guess (Jin et al., 2012).

Thalassinoides burrows. Tyndall Stone Cladding on the Terminal City Club, Vancouver.

Weathered Thalassinoides burrows at the Fairmont Banff Springs Hotel.

Many other fossils are present and abundant in these strata and have been described by Jin et al. (2012). The Receptaculitid Fisherites reticulatus (Finney & Nitecki, 1979) is a spectacular component of this rock, and if it were needed, a distinguishing feature of Tyndall Stone. Up to 25 cm or so in diameter, these are circular fossils with a scaly appearance, appearing like the seed head of a sunflower. They are assumed to be fossilised calcareous algae.

Fisherites at the Terminal City Club (West Cordova Street facade) in Vancouver

Fisherites on the Terminal City Club in Vancouver

A section through Fisherites on the terrace at the Fairmont Banff Springs Hotel

Also present are very large Nautiloids. These include orthocones as thick as my arm and indeed called Armenoceras. This genus along with Endoceras can be over a metre in length.

Large orthoceras sections on book matched slabs at the Fairmont Chateau Lake Louise

Orthoceras on the terrace of the Fairmont Banff Springs Hotel

The coiled Nautiloid Wilsonoceras which can reach diameters of 40 cm is also present.

Section through the chambers of a coiled Nautilus

Section through a coiled Nautilus

These cephalopods are diagnostic of the so-called ‘Arctic Cephalopod Fauna’ and are typical of these late Ordovician carbonate platforms.

Other molluscs include gastropods, such as the planispiral Maclurina and the cone-spiralled Hormotoma.

Tyndall Stone with Thalassinoides at the Fairmont Chateau Lake Louise. A possible planispiral gastropod can be seen at bottom right.

Sections through a gastropod on slabs paving the lobby of the Fairmont Banff Springs Hotel

Corals are also present. This is probably the tabulate coral Catenipora.

Fairmont Chateau Lake Louise

Rugose corals include the varieties Grewingkia, Crenulites and Palaeophyllum.

Rugose Coral on the Terminal City Club, Vancouver

Other reef-forming organisms in addition to corals and Receptaculitids are stromatoporoids of which I found only fragments.

A fragment of a stromatoporoid at the Fairmont Chateau Lake Louise

The Tyndall Stone-type of Thalassinoides facies is regionally widespread throughout the Upper Ordovician strata of Laurentia, with very similar formations existing in Greenland (Børglum River Formation), as well as in Canada and the USA (i.e. Bighorn Dolomite of Wyoming; see Jin et al., 2012; Gingras et al., 2004; Sheehan & Schiefelbein, 1984).

As a good quality freestone, Tyndall Stone has also been used for carving by a number of artists and it even gets a mention in literature. Canadian author Carol Shields described Tyndall Stone in her, perhaps predictably titled, novel ‘The Stone Diaries’; “Some folks call it tapestry stone, and they prize, especially, its random fossils: gastropods, brachiopods, trilobites, corals and snails. As the flesh of these once-living creatures decayed, a limey mud filled the casings and hardened to rock”

Urban Geology guides and descriptions of Tyndall stone buildings in Winnipeg are available by Thorsteinson (2013) and on Donna Janke’s Blog ‘Destinations, Detours & Dreams’.

Tyndall Stone is widely used throughout Canada, but as far as I know, has yet to make it to the UK … I looked at the following buildings during my recent trip to Vancouver and Banff National Park.

In Vancouver, the Tyndall Stone-clad Terminal City Club is on West Hasting’s street and the same building occupied by the Lion’s Pub fronting onto West Cordova Street.

In Banff National Park, the Fairmont Chateau Lake Louise has Tyndall Stone cladding on the ground floor and the Fairmont Banff Springs uses polished Tyndall Stone as paving, cladding and dressings in the impressive entrance hall.

My Sister, thrilled at finding the Receptaculitid Fisherites on the Terminal City Club in Vancouver. It is on the slab above the right side of the porch.

All photos used here are by Ruth Siddall and should be cited as such.

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To cite this article:

Siddall, R., 2017, Tyndall Stone: An Iconic Canadian Building Stone., Orpiment Blog, published 09/09/2017: http://wp.me/p53QQu-bC

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References and further reading

Finney, S. C. & Nitecki, M. H., 1979, Fisherites n. gen. reticulatus (Owen, 1844), a New Name for Receptaculites oweni Hall, 1861., Journal of Paleontology., 53 (3), 750-753.

Gingras, M. K., Pemberton, S. G., Muelenbachs, K. & Machel, H., 2004, Conceptual models for burrow-related, selective dolomitization with textural and isotopic evidence from the Tyndall Stone, Canada., Geobiology, 2, 21–30.

Janke, D., 2017, Winnipeg and Tyndall Stone: Fossils and Architecture., Destinations, Detours & Dreams.

Jin, J., Harper, D. A. T., Rasmussen, J. A. & Sheehan, P. M., 2012, Late Ordovician massive-bedded Thalassinoides ichnofacies along the palaeoequator of Laurentia., Palaeogeography, Palaeoclimatology, Palaeoecology 367–368 (2012) 73–88.

Kendall, A.C., 1977. Origin of dolomite mottling in Ordovician limestones from Saskatchewan and Manitoba. Bulletin of Canadian Petroleum Geology, v. 25, p. 480-504.

McCracken, A.D., Macey, E., Monro Gray, J.M. & Nowlan, G. S., 2007, Tyndall Stone., Natural Resources Canada.

Sheehan, P.M. and Schiefelbein, D.R.J., 1984. The trace fossil Thalassinoides from the Upper Ordovician of the eastern Great Basin: deep burrowing in the early Paleozoic. Journal of Paleontology, v. 58, p. 440-447.

Shields, C., 1993, The Stone Diaries., Fourth Estate., 361 pp.

Thorsteinson, J., 2013, Tyndall Stone., Winnipeg Architecture Foundation Inc., 13 pp.

Gillis Quarries

 

 

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Whales on the Road

This post is a departure from my usual blogs about rocks, minerals, pigments and err … stamps. It is about dead whales touring the country on the back of lorries. There are not many things these days that provide pretty much no hits when Googled, but this subject seems to be one of them. You may well be asking why I would be Googling ‘Whales’ ‘Lorry’ ‘Supermarket Car Park’. Here is the answer.

I was talking to my colleague Jack Ashby at the UCL Grant Museum of Zoology about their upcoming #WhaleWeekender extravaganza, wherein the skeleton of an 8 m long northern bottle-nosed whale will be assembled for the first time since the 1940s. You can read more about this in Jack’s blog here. The whale in question had toured the country before ending up, disarticulated in the Grant Museum. I told Jack that I remembered seeing a whale in the back of a truck when I was a kid in Salford in the early 1970s. Jack looked at me like I had said 1870s. On reflection there is certainly a circus side-show, freak-show element to this experience. Until speaking to Jack, I have not thought about this for years.

I went home and got onto Google, expecting to find photos, local newspaper articles etc., but nothing came up. However I did discover two illuminating pieces about the phenomenon that was whale tours, one in the Guardian and another from the BBC. Both remark that these events went largely unreported, although it seems that they were not uncommon between the 1950s and early 1970s. The touring whales were obtained from Norwegian whalers and were given imaginative names such as ‘Jonah’, ‘Hercules’ and ‘Goliath’, although one was called ‘Eric’.

This picture from the BBC & Pathé shows a whale on tour, probably in the 1960s, with body parts helpfully labelled. Note the instrument of death, a harpoon, at lower right. This was almost certainly taken in the north of England. Look at that roofline. Look at those kids.

The BBC article makes statements such as ‘In an era of limited television, staring at a dead whale was seen as a good pastime’ and ‘Parents took their toddlers to see the carcasses’. Yup. That was me.

I did find some memories via social media, from people of my generation living in my home town of Walkden in Greater Manchester. Many comments were along the lines of ‘Does anyone remember the whale in Walkden? Or am I imagining it?’ The following comments showed that some did remember, many didn’t, but no one had any photos. There seems to be very little evidence that this actually happened. However someone did mention they had seen a mammoth and had a picture to prove it … but that is another story.

For those of us born in the second half of the twentieth century, one is often conscious that one’s memories are influenced by images (so now I am beginning to remember that I may have seen the mammoth too …) but I can safely say that this is not the case with the Walkden whale. This is what I remember. I was very young at the time, probably between 5 and 7 years old, which would put this event at between 1972-1974. My dad had heard about this whale and said ‘shall we go and have a look at it?’ So off we went to Scan car park where the whale truck was pulled up. Scan was a hypermarket, the first one in our area and it was located just off Manchester Road in Walkden (it is now a branch of Tesco). I remember it was rainy and misty. It could have been Winter, it could have just been Salford. There were not many people there. I suppose my Dad paid someone.

And there it was in the back of a lorry with the sides let down. A whale, huge and black, maybe 10 or more metres long. It was a big truck. It didn’t look real, it looked like it was made of a hard, black plastic. I asked my Dad if it was real (whilst keeping tight hold of his hand) and he replied ‘Oh yes, of course it is’. I don’t have any memory of smell (but I think that’s just me, I don’t have any memories of smell at all). In retrospect I suspect it was coated with tar or something. I have no idea what species of whale it was. All I really remember was its eye. I just remember staring at its eye. I imagined whales to have big eyes but this was small and beady, surrounded by folds of flesh. I seem to remember the lorry was blue. We looked at it for around ten minutes and then left. I haven’t really thought of it since. My Dad was a very keen photographer and in retrospect I am astonished he did not bring his camera and take a photo. I don’t have any memories of a photo, but perhaps I should scour my Dad’s slides and negatives. You never know.

Sadly my Dad died ten years ago. I phoned my Mum, wondering if I could extract any further information, and this is how the conversation went

Me: Do you remember Dad and me going to see the whale?

Mum: In Wales?

Me: No, in Scan.

Mum: In Wales??

Me: No, in Walkden, a whale – not Wales

This went on for a while, alliteratively, but sadly Mum had neither recollection of my Dad and me going to see it, nor any memory of a photo recording the event (NB My Mum now lives in Wales). I am beginning to wonder if I imagined this too – were it not for the fact that it is the only non-skeletal whale that I had ever seen until the 1990s and I can see its dead eye in my mind now.

[NB: The whale I saw in the 1990s was a dead, beached whale on the island of Mull. I don’t remember how that smelled either, but it must have been shocking].

I would love to hear from anyone who does remember the Walkden whale, but I am also interested to hear from anyone else who remembers other whale tours, despite them being something that can be gladly consigned to history. #WhaleMemories

 

 

Barnicoat, B., 2015, The mystery of Jonah, the giant whale who toured the UK in the 1950s., The Guardian, Wednesday 8^th July.

Bell, B., 2016, When dead whales went on tour., BBC News Online, 1^st May. 

Photograph of a whale’s eye is from http://www.whalesforever.com/whale-senses-sight.html

 

Inside the Bartlett Brick

The new building at 22 Gordon Street houses The Bartlett School of Architecture. Completed in 2017 and designed by Hawkins\Brown Architects, the building has recently been named on the shortlist for The Architect’s Journal AJ100 Building of the Year prize and the RIBA London Awards. The structure is a retrofit of the former Wates House, the ghost of which still exists in the core of the building. What replaces it is a spacious, fit-for-purpose building for the UCL School of Architecture.

Now those of you that know me and know that my interests in the fabric of UCL are mainly biased towards the use of stone, may have assumed that I was disappointed to see a brick and concrete structure appear on the corner of Gordon Street and Endsleigh Gardens. Not so. I declare a fondness for both materials, though I confess to prefer my concrete to be around 2000 years old, the bricks used to clad 22 Gordon Street are rather special.

I am very grateful to the Bartlett’s Kevin Jones for supplying me with a specimen of ‘The Gordon Street Klinker’ a brick made specially for the construction of the building by the German brick makers Janinhoff.

Janinhoff make a great deal of bricks of different compositions, but mainly to a standard size. The Gordon Street Klinker is slimmer and longer than the standard bricks in their repertoire. 140,000 of these bricks, measuring 290 x 52 x 70 mm were used on the façade.

The brick is water-struck and twice fired. The water-struck brick making process works well for high moisture content, high plasticity clays. The clay is ‘struck’ in a wooden mould, and the large amount of water present allows for the mould to be easily removed, without the clay sticking to it. Evidence of this process can be seen in the puckered, ‘troweled’ surface of these bricks and the lip from clay overhanging the top of the mould. Lower water content clays need to be ‘sand-struck’; i.e. the mould is coated with sand which stops the brick from sticking to it.

Evidence that these bricks are hand made can be seen in this example from the Endsleigh Gardens façade of the Bartlett’s 22 Gordon Street Building …

Look closely and you can see the brick maker’s fingerprints …

Janinhoff fire their bricks in a circular, so-called Hoffman Kiln which can operate continuously. Patented by Friedrich Hoffmann in 1858, these are the standard brick kilns used worldwide today. They are large circular or oval structures often with a central chimney. The interior has firing chambers radiating out from the central space (below the chimney). The kilns are fired by a movable ‘fire wagon’ which can travel on rails around the interior, firing each chamber consecutively.

The Gordon Street Klinker is coal fired at maximum temperatures of 1200°C. Looking at the surfaces of the bricks, ‘firing ghosts’ are seen patterning the surface of the bricks. This tells us how they were stacked in the kiln, subtly changing the oxidation of the brick surfaces where they touch each other.

Above: Janinhoff’s Hoffmann kiln, showing bricks being stacked ready for firing and also note the use of spacers and other kiln furniture.

The grey colour of the bricks indicates a low-iron content clay. Such materials are available in the northern Germany and Denmark deposited as Quaternary glacial clays. The Jutland Peninsula lay at the southern edge of the ice sheet during the last glaciation and the clays were deposited as the ice sheet retreated between 20 – 10 thousand years ago.

To be workable, reduce shrinkage and cracking on drying and firing and be strong, brick clays need to contain inclusions or temper. Inclusions are natural mineral grains that occur naturally in the clay whereas a temper is added by the brick makers and can include both mineral and organic particles.

To look inside the Bartlett bricks it is necessary to produce a thin section, a slice 30 µm thick for observation using polarising light microscopy. This technique is routine in geology for examining rocks and identify their component minerals. As ‘synthetic stones’, ceramics may also be analysed in this way under the discipline of ceramic petrology.

Under the microscope, the Bartlett bricks have an almost isotropic (opaque) clay matrix indicating that the clay minerals have broken down and have begun to melt. This indicates that the brick has been fire in excess of 1000°C (and indeed we are aware from the manufacturers that temperatures of 1200°C were attained). It is not possible to distinguish whether or not the brick clay contained inclusions or it has been tempered, or perhaps both! Mineral particles present are dominantly quartz, but chert, feldspar and zircon are also present, indicating granitic rocks in their source. Grains are poorly sorted ranging from very fine (a few 10s of microns diameter) to particles of around 0.5 mm, the latter just visible to the naked eye. It is reasonable to expect that the finest portion are naturally occurring inclusions in these glacial clays.

The photomicrographs below show the brick photographed in plane polarised light and under crossed polars, x 40 magnification.

The mineral grains are sub-rounded to sub-angular, indicating a natural sand source (i.e. not mechanically crushed). The composition is clearly granitic as indicated by the feldspar, zircon (this in typically tiny grains) and the large quartz grains with fluid inclusion trails. Some of these features are seen in the photomicrographs below. Left, the large grain in the centre is a feldspar; x 40 magnification, the field of view is ~ 3.5 mm. Middle and Right, quartz grains with inclusion trails, x 100, the field of view is ~ 1.5 mm.

Citation

Siddall, R., 2017, Inside the Bartlett Brick, Blog: Orpiment https://orpiment.wordpress.com/2017/06/02/inside-the-bartlett-brick/

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Geology on Postage Stamps: #1 Energy Resources, Great Britain 1978

This set of GB commemorative stamps was issued on 25^th January 1978, the first issue of commemoratives for that year. The make the link between energy and geology in a world when alternative energies were a mere twinkle in most peoples eyes.

They were designed by Peter Murdoch (b. 1940) and depict symbols representing energy; oil, coal, gas and (nuclear) electricity coupled with stylised depictions of geological structures and strata associated with hydrocarbon reserves.

The stamps were printed by Harrison & Sons for the Post Office.

First I was afraid, I was petrified … A short history of scary silicified log cabins

This is urban geology at the extreme; petrified wood is not exactly a common building stone, though it is becoming more frequently seen as a decorative stone, used for interior feature walls and even chopping boards and coasters. However it does have a place as a building stone, albeit mostly for novelty purposes … and only in America. Or at least this is the case as far as I am aware.

Silicified or petrified wood is relatively common and always an attractive fossil, with excellent preservation of the wood structure down to cell level. Identification of wood down to species level is often possible from microscopic observation of preserved cell structure. Trees have been around since the Carboniferous but are often much ignored in earth history. They are the background to what are perceived to be more interesting events. Here is an Upper Cretaceous scene whereby a right porker of a Tyrannosaurus is bringing down a green skinny lizard as an amuse bouche, whilst being eyed by circling Pterosaurs. These trees in the background are probably Araucaria sp.

The process of silicification of wood is frequently closely associated with local volcanism. Silica is leached from decaying volcanic ash and carried in groundwaters and stream waters where it can permeate logs and branches. This works particularly well if the logs are buried in ash. Many fossil forest deposits represent preserved log jams in river systems and tree debris becomes silicified in anoxic environments (see Sigleo , 1979). Colours are imparted by trace elements; iron, copper, manganese, even uranium. Black is produced by carbon or finely disseminated pyrite.

Silicified wood deposits are known from Chemnitz in Germany from the Permian Leukersdorf Formation (Luthard et al., 2016) where the coloured stones were used as decorative inlay and as semi-precious gemstones. Also in Europe, deposits occur in Lesvos in Greece (Miocene; see Vasileiadou & Zouros, 2012). Worldwide, silicified wood is known from China (i.e. the Cretaceous ‘Jehol Biota’; see Ding et al., 2016) and exceptionally well-preserved, Pliocene trees are found in Java, Indonesia and Triassic trees occur in Madagascar, and these regions are the origin of most silicified woods on the decorative stone market today (Mandang & Kagemori, 2004; Yoon & Kim 2008). Recent discoveries petrified trees have been made in Brazil (Lower Permian tree ferns; see Maria da Conceiçao et al., 2016) and Turkey (Miocene willows, junipers and oaks; see Akkemik et al., 2016).

Silicified wood panelling supplied by the Emperors of Stone Bling, Maer Charme.          Photo by Ruth Siddall.

There are a large number of deposits of various ages in the USA and it is here that fossil trees have largely been used for building. Deposits are known from the Dakotas, Colorado, Oklahoma, Texas etc. The best known deposit is in the Upper Triassic Chinle Formation represents continental facies and outcrops throughout the southwestern USA. These famous fossil conifer deposits occur in the Lower and Upper Petrified Forest Members of Carnian-Norian age. Conifer logs are also found in the intervening Sonsela Member, representative of an alluvial floodplain (see Ash, 1992; Trendell, 2013). However, there are many other examples through the West and Midwest. Many of these deposits have been raided for garden ornaments and other small-scale structures.

A well-known and rather American Gothic building constructed from petrified wood is the (former) gas station in Lamar, Colorado, described by David Williams in his book ‘Stories in Stone’ and also illustrated in his blog. The gas station was built by one William Brown in the 1930s. The Colorado trees are of Cretaceous age but the precise age of strata of origin is unknown. The ‘logs’ were found in fluvial outwash in farmland around 25 miles south of Lamar.

Lamar Gas Station; photo from Geologywriter.com

And then there is Petrified Wood Park in Lemmon, South Dakota, also constructed in the 1930s. This is a truly terrifying place; cones, pinnacles, pyramids and creepy-looking grotto-like buildings are built from petrified wood as well as dinosaur and mammoth bones. The park occupies a whole block of the town and was built by amateur geologist and ‘visonary’ Ole S. Quammen. To be fair his intention was altruistic, it was to provide work for 50 or so otherwise unemployed men during the depression era West. Quammen’s heirs donated the park to the grateful town of Lemmon in 1954 where it remains ‘the world’s largest petrified wood park of its kind’. Obviously. An on-site museum once house a collection of stuffed animals playing musical instruments. Sadly, these are no longer on display. The petrified wood was sourced locally, potentially from several strata. The Early Cretaceous Lakota Sandstone Formation outcrops in the eastern Black Hills and has fossilised logs of cypress, palm and cycads. The Hell Creek Formation of South Dakota also has petrified Late Cretaceous cypress (and dinosaurs). The Palaeocene petrified wood is found in the Badlands of South Dakota where conifers and broadleaf tree trunks and branches are preserved (Teachout, 1995).

Lemmon Petrified Wood Park sign; photo from SouthDakota.com

According to Snider (2012), Texas is the state for construction in petrified wood, and she cites Austin, Huntville, Decatur (which also has a petrified wood gas station) and Stephenville as all having buildings incorporating this unexpected stone. However, the town of Glen Rose in Somerville County has over 40 buildings and other structures constructed of silicified wood. It was once known as ‘The Petrified City’. The post office, several houses, fountains, a (now disused and ruined) speakeasy and the bandstand are all built from petrified wood. The bandstand also incorporates slabs with spectacular dinosaur footprints too.

The ruins of Glen Rose’s speakeasy; photo by Tui Snider (2013)

Bandstand, Glen Rose, Texas; photo by Tui Snider (2012)

Detail of dinosaur footprint in Glen Rose’s bandstand; photo by Tui Snider (2012)

The origin of this Texan petrified wood building spree, which occurred in the 1920s and 30s was a unexpected consequence of the mechanisation of agricultural machinery. Farmers were able to dig deeper into their soils than before and they hit a petrified wood motherlode in the local fields. The logs were hauled out and used to build the town.

Finally, the most attractive structure built from petrified wood is not all scary. It is Agate House, located in the Petrified Forest National Park, Arizona. It was originally constructed between 1050 and 1300 AD by Ancestral Puebloans from Triassic Chinle Formation petrified trees. Other examples of structures built from petrified wood have also been excavated in the surrounding region, since the 1930s. The excavation of Agate House and its subsequent reconstruction was overseen by archaeologist Cornelius Burton Cosgrove Jr. (1906 – 1999). Petrified wood was also used for arrowheads and similar artefacts by the Ancestral Puebloans.

Above, Agate House; photo by Amusing Planet

Above, the wall of Agate House; photo by NotsofastinBoulder’s Blog.

More petrified wood buildings in the USA …

Gas Station, Decatur, Texas

Carter County Museum, Montana – does anyone have a photo of this? It is partially built of Hell Creek Formation wood.

Petrified wood and petrified wood buildings in Oklahoma

Outside the USA …

The town of Mata – “Cidade da Pedra que foi madeira” (“The city of rocks that once were wood.”) – in Rio Brande do Sul, Brazil. Petrified wood from the Upper Triassic Caturrita Formation is used to build several buildings and can be seen in the Palaeobotanical Garden. The fossils were collected by priest and palaeontologist Daniel Cargnin.

Thanks to Christian Kammerer @Synapsida for this information and photos.

 

If anyone knows of any more structures built of petrified wood outside the US, do let me know …

 

How to cite this blog:

Siddall, R., 2017, First I was afraid, I was petrified … A short history of scary silicified log cabins., Orpiment Blog https://orpiment.wordpress.com/2017/04/13/first-i-was-afraid-i-was-petrified-a-short-history-of-scary-silicified-log-cabins/

 

References

Akkemik, Ü., Arslan, M., Poole, I., Tosun, S., Köse, N., Kiliç, N. K. & Aydin, A., 2016, Silicified woods from two previously undescribed early Miocene forest sites near Seben, northwest Turkey., Review of Palaeobotany and Palynology 235., 31–50.

Ash, S.R. and Creber, G.T., 1992. Palaeoclimatic interpretation of the wood structures of the trees in the Chinle Formation (Upper Triassic), Petrified Forest National Park, Arizona, USA. Palaeogeogr., Palaeoclimatol., Palaeoecol., 96:299 317.

Ding, Q., Tain, N., Wang, Y., Jiang, Z., Chen, S., Wang, D., Zhang, W., Zheng, S., Xie, A., Zhang, G. & Liu, Z., 2016, Fossil coniferous wood from the Early Cretaceous Jehol Biota in western Liaoning, NE China: New material and palaeoclimate implications., Cretaceous Research, 61, 57-70.

Mandang, Y. I. & Kagemori, N., 2004, A Fossil Wood of Dipterocarpaceae from Pliocene Deposit in the West Region of Java Island, Indonesia., Biodiversitas, 5(1), 28-35.

Maria da Conceiçao, D., Saturnino de Andrade, L., Cisneros, J. C., Iannuzzi, R., Pereira, A. A. & Machado, F. C., 2016, New petrified forest in Maranhao, Permian (Cisuralian) of the Parnaíba Basin, Brazil., Journal of South American Earth Sciences 70, 308-323.

Petrified Wood Park, Lemmon, South Dakota.

Petrified Woods from the Indonesian Islands of Java and Sumatra.

Saltarelli, M, G., 2009, ‘Irreplaceable Works of Art’: Petrified wood treasures and dinosaur tracks create a paradise of geology.

Sigleo, A.C., 1979. Geochemistry of silicified wood and associated sediments, Petrified Forest National Park, Arizona. Chem. Geol., 26: 151–163.

Snider, T., 2012, Texas Road Trips: From Dinosaurs to Drive-Ins.

Snider, T., 2013, A to Z Texas: P is for Petrified Wood Buildings.

Teachout, G. E., 1995, Petrified wood of South Dakota.

Trendell, A. L., Nordt, L. C., Atchley, S. C., Lebland, S. L. & Dworkin, S. I., 2013, Determining floodplain plant distributions and populations using paleopedology and fossil root traces: Upper Triassic Sonsela Member of the Chinle Formation at Petrified Forest National Park, Arizona., Palaios, 28, 471-490.

University of Arizona, Laboratory of Tree-Ring Research; Fossil Trees or Petrified Wood.

Vasileiadou, K. & Zouros, N., 2012, Early Miocene micromammals from the Lesvos Petrified Forest (Greece): preliminary results., Palaeobio. Palaeoenv., 92, 249–264.

Williams, D. B., 2009, Chapter 7: Pop rocks, pilfered fossils and Phillips Petroleum – Colorado Petrified Wood., Stories in stone: travels through urban geology., Walker Publishing Inc., New York., 133-151. & Blog.

Yoon, C. J. & Kim, K. W., 2008, Anatomical descriptions of silicified woods from Madagascar and Indonesia by scanning electron microscopy., Micron 39, 825–831.