Archive for June 22nd, 2014

Wooster Geologist in London at the British Museum

June 22nd, 2014

Front BM 062214LONDON, ENGLAND — I arrived late last night in London after a series of delays in my departure from Poland, so I was pleased that today was a Sunday so I could chill a bit before work with Paul Taylor tomorrow. If I can visit one place in London (other than the Natural History Museum, of course) it is always the British Museum (above). As you can see, the weather was spectacular — and the crowds took advantage of it. I thought I’d just highlight a set of exhibits that is very cool, despite the fact that few visitors seem to spend much time with it.

Enlightenment textIt is the “Enlightenment: Discovering the World in the Eighteenth Century” gallery. I think it is well done and highly evocative, at least for scientists. My favorite part is there on the right end: “The Natural World”.

Enlightenment cabinetThe cases are deliberately old-timey to evoke the “cabinets of curiosity” 18th Century polymaths had for their collected treasures. In fact, some of these cabinets themselves date back to that period. Here we see rocks, fossils, plants and animals collected by Enlightenment explorers, philosophers, historians, and just plain rich guys. These were the very specimens that thrilled and puzzled some very great minds — not that we don’t have plenty of mysteries remaining about them.

Mastodon BM 062214This is a mastodon jaw (Mammuthus americanum) collected “near the Ohio River” and given to the museum in 1768. It was called “The Unknown American” and thought to be from some extinct carnivorous elephant-like beast.

Smith fossils BM 062214My favorite set of fossils here was collected and used by the famous William “Strata” Smith (1769-1839)  in his pioneering work on geological correlation and mapping. Fossils like these were crucial to working out the relationships of rock layers (“strata”) and early concepts of Earth history. There is something inexplicably enchanting about seeing objects handled by past luminaries.

Schist sarcophygusOn an unrelated but geological note, I have a complaint about a small number of the displays. This ancient Egyptian sarcophagus is an example. What is the rock type here? I’d say a basalt or maybe a fine-grained granodiorite (like the Rosetta Stone).

Schist closer BM 062214Here’s a closer view of the sarcophagus. The sharpness of the carving shows how fine-grained and massive this rock seems to be. (I know the rules — no scratching the artifacts to test their properties.) But what does the sign say?

Schist signBlack schist? No way. Schist is foliated and flakey and most decidedly not massive and so superbly suited to carving. Maybe someone will correct my notion of “schist”, but right now I’m certain this part of the label is wrong. I’ve seen this fairly often in museum displays: the rock types given don’t always match what appears to be the actual lithologies. Not enough geoarchaeologists to go around, I suppose.

Romano British hed 062214Here’s a cool Romano-British sculpture that did have a proper identification as “limestone”. (And to be fair, most are correctly labeled.) I liked this artifact in particular because you could look closely at the broken bits —

Ooids 062214The rock is made primarily of these little calcitic spheres called ooids. I would not be at all surprised to learn that this is a Portlandian (Upper Jurassic) limestone from southern England.

It was a fun day at one of the world’s finest museums. Tomorrow I begin work at another.

Wooster’s Fossil of the Week: A silicified rhynchonellid brachiopod from the Permian of West Texas

June 22nd, 2014

Rhynchonellid crura Permian Texas 585Sometimes fossils can be more useful when broken than whole. Above is a much-abused rhynchonellid brachiopod from the Road Canyon Formation (Middle Permian, Roadian, about 270 million years old) found in the Glass Mountains of southwestern Texas. It is part of a set of silicified fossils we etched out of a block of limestone in the last century. The shell has been replaced with resistant silica, so it was easy to extract from the limestone matrix with a long bath in hydrochloric acid that dissolved the carbonate but left everything else. The fossils are like delicate little glass husks. We’ve featured them in this blog several times.

Update: Matt Clapham kindly corrected me in the comments, and it is worth repeating in the text: “It’s Stenoscisma. The large spoon-shaped projection is actually called a spondylium, formed from merged dental plates and it’s quite distinctive for the Stenoscismatidae. The crura are broken but still visible in your specimen; they are the little struts parallel to the narrowest part of the spondylium. There are five Stenoscisma species that appear common in the Road Canyon Formation and yours looks most similar to Stenoscisma triquetrum to me (weakly sulcate with ribs that are somewhat subtle but still extend near the beak).” I made a bonehead mistake labeling the spondylium incorreectly, hence the “c”. Here’s to the value of Twitter, blogging, and knowledgeable colleagues!
Rhynchonellid Permian Texas 585Here’s the dorsal side of the specimen for completion. The exterior is in poor shape.

I’d love to identify this specimen to at least the genus level [update: see above and the comments!], but there is not enough detail preserved, at least for my skill set. The Permian brachiopods of West Texas were famously studied by G. Arthur Cooper and Richard E. Grant in the 1960s and 1970s. The numbers of species are overwhelming in this ancient reef system, and almost all of them are preserved in this delicate way.

References:

Cooper, G.A., and Grant, R.E., 1964, New Permian stratigraphic units in Glass Mountains, West Texas. American Association of Petroleum Geologists Bulletin 48: 1581-1588.

Cooper, G.A., and Grant, R.E. 1966. Permian rock units in the Glass Mountains, West Texas, In: Contributions to stratigraphy, 1966: U.S. Geological Survey Bulletin 1244-E: E1-E9.

Cooper, G.A. and Grant, R.E. 1972. Permian brachiopods of West Texas, I. Smithsonian Contributions to Paleobiology 14: 1–228. [and five other volumes]

Olszewski, T.D. and Erwin, D.H. 2009. Change and stability in Permian brachiopod communities from western Texas. Palaios 24: 27-40.