Stonesfield Slate, Fossil Exhalations, and William Buckland

The quarry area in the small town of Stonesfield, Oxfordshire, England, has been called the “best Middle Jurassic terrestrial reptile site in the world.” Stonesfield is also the place of origin for what would be the first formally described dinosaur, Megalosaurus. From my perspective, the region’s other claim to fame is the Stonesfield slate, first used in Roman times when the famous builders roofed their homes with the local rock.

Welsh naturalist Edward Lhuyd was the first to describe fossils from Stonesfield. In his 1699 Lithophylacii Britannici Ichnographica, he illustrated two teeth, one of which he described as that of a fish. Lhuyd believed that fossils formed from “exhalations which are raised out of the sea” carrying fish-spawn that got caught in chinks in the ground and became fish fossils. He added that such fossils “have so much excited our admiration, and indeed baffled our reasoning.”

But the Stonesfield didn’t become truly famous until the 1800s and the discoveries and descriptions of William Buckland. One of my all-time favorite geologists, Buckland was an ordained priest in the Church of England; notorious for eating practically everything; one of earliest professional geology instructors, at Oxford University; a fellow of the Royal Society; and the first to recognize the importance of coprolites (he coined the term). His eccentricities earned him a famous description by Charles Darwin, who wrote of Buckland: “though very good-humoured and good-natured [he] seemed to me a vulgar and almost coarse man. He was incited more by a craving for notoriety, which sometimes made him act like a buffoon, than by a love of science.” Oh Charles, don’t be so stuffy.

William Buckland

We do not know exactly when Buckland obtained his famous fossils because he failed to jot down this fact. Those who have studied the issue have put the date as no later than 1818, due to an 1824 article by Georges Cuvier. No matter when he found them, Buckland made a formal description of a lower jaw, teeth, and a huge thigh bone on February 10, 1824, at a presentation to the Geological Society in London.

Buckland ascribed his fossils to a carnivorous reptile at least forty feet long and weighing as much as an elephant. In honor of its larger-than-life size, at least larger than any known land animal, he named it Megalosaurus, the Great Lizard. Twelve years later, Richard Owen would include Megalosaurus, along with Iguanodon and Hylaeosaurus, in his new order of animals, Dinosauria.

The Megalosaurus tooth and jaw of Buckland

Curiously, the so-called Stonesfield slate isn’t slate, which makes sense considering the source rock is so fossiliferous. It is, in fact, limestone, deposited in a shallow marine environment. The bones most likely washed into the water followed by rapid burial by sand transported offshore during storm events. Other fossils found in the quarries include fish, reptiles, mammals, ammonites, bivalves, gastropods, insects, and 13 species of terrestrial plants.

Stonesfield slate from www.gowildgardening.co.uk/buildings.htm

Quarrymen split the Stonesfield slate in a rather nifty manner. Instead of using hammer and chisel, the men relied on cold weather. They would pull the limestone out of the ground (20 to 70 feet deep) in a rough block called a “pendle” and let it sit in a field and absorb water. To ensure moisture retention, the quarrymen would pile dirt atop the blocks and/or douse the stone in water. Over several cold winters, water would penetrate the bedding planes and split the stone into usable pieces. In some cases the split piece would be round and be dubbed a potlid. Builders highly prized the thin slabs of Stonesfield slate, using them in colleges at Oxford.

Recently, English researchers have taken a new look at Megalosaurus and its family Megalosauridae (Palaeontology, v. 51, no. 2, 419-424). They have concluded that the family should be discontinued because of a lack of clear evidence allying the genera that have previously been listed as Megalosauridae. The only reptile that is clearly “megalosaurid” is the one found by Buckland. Perhaps Mr. Darwin should have been more generous in his observations.

Texas Marble...From Maryland

Someone stole my story. Well, not really. It’s mostly a wee fit of jealously at Brian Fisher Johnson, who has a first rate article on building stone in the January issue of Earth magazine. Stretching from Ballykilchine, Ireland, to the Washington Monument, the story tells of the marble quarries and quarrymen in Texas, Maryland, and their contribution to leaving “a very material impression on the face of America.”

Brian’s story focuses on an archaeological dig run by Stephen Brighton of the University of Maryland, College Park. Brighton has been studying the Irish immigrants who left Ballykilchine and traveled to a small settlement a bit north of Baltimore. By around 1860, Texas—so named for a volunteer regiment, the Texas Greens, established for the Mexican-American War—had 600 people. Brighton says that the Irish came for the calcite, in the form of marble for quarrying and limestone for burning.

Little remains from the heyday of the Irish in Texas. Little is also available in the history books, which is what led Brighton to investigate. “It’s a huge gap…in understanding the Irish diaspora,” he says. What he has been able to piece together is unusual. The Irish stayed in Texas for generations, in contrast to the more typical dispersal out from the original center.

Brighton and his students began their dig in July 2009. Their major find was a outhouse, as well as coins, a lice comb, and numerous pieces of glass. He and his students will continue to study their artifacts in order to better understand this unusual group of immigrants.

Brian reports that the value of Texas stone was reported as early as 1811. Quarrying began in 1834 with 13 quarries opened up by 1847. Geologists call the stone the “Cockeysville Marble,” for a nearby town. First deposited 500 million years ago as limestone, the white stone turned to marble around 240 million years ago during the assembly of Pangaea.

Library of Congress description “Washington Monument as it stood for 25 year,” photographed by Mathew Brady circa 1860

The color and location of the marble led it to be the first building stone of any large amount sent by rail to Washington D.C. In 1845, builders began to use the marble from Texas in the Washington Monument. They had put up 152 feet by 1854, when money ran out. Work began again in 1879, with marble from Lee, Massachusetts, but it was too costly, so the rest of the monument was finished with marble from Cockeysville, which accounts for the color change in the big edifice.

Texas marble also went into the “porticoes of the House and Senate wings of the U.S. Capitol building and the towers of St. Patrick’s Cathedral in New York City,” writes Brian. He has written a nifty story about stone once again revealing the connection between people, geology, and history.

Quincy - The Granite City in the Globe

The Boston Globe ran two stories today about the town of Quincy (pronounced Quin-zee) and its granite-influenced past. For nearly two centuries, Quincy supplied granite to great and small buildings of Boston and beyond. These include the dry docks in Charlestown, Massachusetts, customhouses in New Orleans, Boston, and Mobile, Alabama, and the Bunker Hill Monument, a use which led to the first commercial railroad in the United States.

One story focuses on the efforts of locals to draw more attention to the importance of granite to a town once known as The Granite City. They hope to build a Quincy Quarry and Granite Workers Museum but despite a nearly two-decade old agreement to build it, they have had no luck. The story quotes Vic Campbell who said “It seems that when it comes to the Adamses, nothing that anyone can think of is too much. When it comes to the quarries, nothing is too neglectful.’’ As someone who has written about the beautiful and historical Quincy stone and its human and geologic history, I am sad to see that so many seem to not care about their past.

The second story, Of Granite, Plugs, and Feathers, tells the history of the quarries, tracing its earliest use to around 1754 and the King's Chapel, still standing in Boston. Stone was quarried not from the solid walls of rock but from boulders, which masons split by heating with fire and cracking with heavy iron balls. Not until around 1803 did a truly effective manner of quarrying come along. The plug and feather technique originated with a man known as Mr. Tarbox, who introduced the method of drilling holes in the rock and then putting a metal wedge, or plug, surrounded by two L-shaped shims, the feathers, into the hole. Hammering a row of plugs and feathers forced the stone to split apart. Tarbox's method dropped the price of split stone by 40 percent and helped launch Quincy's long history as a granite supplier.

Let's hope that these stories can help with the development of the Quincy museum. Perhaps it will also help with my push for a Slow Stone, my movement to encourage the use of locally quarried stone.

Duke City Stone – Part 2

After visiting some of the Duke City’s less inspired buildings I want to explore a couple of structures that caught my interest not just for their stone. My favorite building is the Cathedral of St. John. I am a sucker for sandstone, especially when completed in an historical style. Austin describes the cathedral as Brick Gothic with a dash of typical Anglican. No matter what one calls it, the church is modest, simple, and grounded. I also like the cathedral because the stone is structural and not a skin or curtain, hung merely for adornment.

Built in 1884, it has a 1930 addition, as well as a renovation from 1951. The all southwestern stone is mixed throughout to give a bit of a look of tartan. Austin suspects that the darkest sandstone comes from quarries near Las Vegas, New Mexico, not Nevada, and dates back to the late Pennsylvanian-early Permian. Much younger and much lighter is the late Cretaceous Mesaverde Formation. It is also much weaker and spalls abundantly along the base of the cathedral. Back at the entrance to the Cathedral House, you can find a third stone, the Coconino Sandstone, one of the legendary layers within the Grand Canyon. It is 275 million years and formed in a vast dune field.

Moving a bit away from my goal of looking beyond the stone, I want to point out the nifty butterfly or bookmatched pattern of an easily overlooked box around the block from the Cathedral. Austin doesn’t note the origin of the stone but does stop to point it out, I think mostly because it is a way to use geology that should be noticed more often.

Finally a quick turn to what started life as the First National Bank building. Built in 1922, it is the Duke City’s first skyscraper and first building with a steel infrastructure. Austin called it the First Security Bank, and now it is designated the Sunrise Bank building (one wonders how soon till another bank nabs the building). It looks like hundreds of buildings with lower floors set off from the upper levels by a color or material change. There is little stone used. A whitish granite from the Raymond quarries in the Sierra Nevada is the most noticeable.

Thus ends my short tour of Albuquerque and its building stone. I highly recommend that if you do go there to try and pick up a copy of George Austin’s guide. It is one of the best and most thorough written not only about specific building stone but also about the industry, quarrying, and fabrication.

South to Albuquerque for stone

Continuing my exploration of building stone in New Mexico, I traveled down to Albuquerque, aka Duke City. (One quick side note, I took the new commuter train between Santa Fe and Albuquerque. The Rail Runner Express runs regularly between the two cities and is a fun way to travel.) But back to the rock in the Duke City, where I benefited from George Austin’s excellent guide book: Albuquerque downtown from a geologic point of view—A walking tour of the city center. It is published by the New Mexico Bureau of Mines and Mineral Resources in their series Scenic Trips to the Geologic Past.

I have written about Austin’s book before but this was the first time I had a chance to use it. Today I will focus on how Albuquerque architecture illustrates one of my favorite maxims about building stone geology: Even if the architecture is boring, the stone makes the building worth seeing.

For example, the AT&T building exemplifies banal architecture but the designers clad the bottom in a quite handsome pink granite from Texas. Known in the trade as the Town Mountain Granite, and informally as Fred Red (from the quarrying site, Fredricksburg), the stone is part of the extensive Llano Uplift, a 9,000 sq. km exposed section of Laurentian rocks in central Texas. Fred Red is a little over a billion years in age. On the AT&T building the slabs have both a polished and flamed finish. A flamed finish is produced by passing the stone under a plasma torch, which explodes the surface minerals to produced a textured surface.

Fred Red and AT&T. Note how the two surface treatments creates an illusion of using two different stones.

(The Fred Red and other granitic cohorts from the Llano will be addresses in the January/February 2010 GSA Bulletin. A new analysis shows that they are not A-type granites as previous workers described. Instead they formed from a continental collision between North America and “an unknown continent that left the scene before it could be identified,” according to the press release. I suspect that any information about the unknown assailant would be appreciated!

City Hall also highlights my maxim. This time the stone is a local rock, Apache Golden Vein, quarried near Belen, New Mexico. Geologists know it is as the 340-320mya Madera Formation. Fossil rich, including crinoid stems, clams, and bryozoans, the Apache also has mustard-colored styolites, which Austin notes are “post-depositional, pre-quarrying” and produced from oxydized, porous clay. Once quarried, the panels fade from weathering.

City Hall above and the nifty panels of Apache Golden Vein below.

And finally, at least on my tour de ugly, is the Bernallilo County Courthouse. Again you can find Apache Golden Vein panels, but the more numerous panels are a concrete mixed with chunks of obsidian. Austin reports that they are not local. I note them because it is so unusual to see obsidian as building stone. In fact, I don’t know of any other buildings built with obsidian. Does anyone?

Obsidian chunks in a concrete matrix.

Later this week I will describe some of the buildings I liked not just because of their stone.