Sunday, December 9, 2018

Ordovician updates

A few miscellaneous items to clear out of my Ordovician inbox, involving new members of Club Late Ordovician, conulariids, and pseudofossils:

Camp Nelson National Monument

Since we were introduced to Club Late Ordovician two years ago, two more parks have joined this exclusive organization for National Park Service units that include fossiliferous Upper Ordovician rocks. One is Saint Croix National Scenic Riverway, thanks to some isolated occurrences of the Platteville and Decorah that were protected from erosion by ancient faulting along the St. Croix Valley. These outliers represent the most northerly and landward outcrops of these formations, and are worth a post of their own at some point. The other new member is the newest NPS unit, Camp Nelson National Monument in Kentucky.

Right on cue, it's a map with a giant caption! (It's the map from the 2016 post with the two new points added, #9 and #14.) 1. Death Valley National Park; 2. Great Basin NP; 3. Yellowstone NP; 4. Grand Teton NP; 5. Bighorn Canyon National Recreation Area; 6. Big Bend NP; 7. Chickasaw NRA; 8. Mississippi National River and Recreation Area; 9. Saint Croix National Scenic Riverway; 10. Pictured Rocks National Lakeshore; 11. Effigy Mounds National Monument; 12. Buffalo National River; 13. Hot Springs NP; 14. Camp Nelson NM; 15. Stones River National Battlefield; 16. Natchez Trace Parkway; 17. Katahdin Woods & Waters NM; 18. Saratoga National Historical Park; 19. Delaware Water Gap NRA; 20. Chesapeake and Ohio Canal National Historical Park; 21. Denali NP & Preserve. The grey blob is the known extent of the Deicke K-bentonite.

Camp Nelson is rather more famous for its Civil War history, but the Camp Nelson area is also notable for its geology. In fact, per Andrews (2005), "Because of the quality of exposures, accessibility, and the importance of the site in research and geologic education, the Kentucky Society of Professional Geologists has named the Camp Nelson area as Distinguished Geologic Site 2."

The park overlays four Ordovician formations, in ascending order the Camp Nelson Limestone, Oregon Limestone, Tyrone Limestone, and Lexington Limestone (Wolcott 1969). They are all examples of your classic marine Ordovician limestones; no points for guessing that brachiopods and nautiloids are implicated in Camp Nelson NM joining Club Late Ordovician. (Not surprisingly, these limestone formations are also karst-formers, and caves and sinkholes are common in the area.) The Tyrone Limestone is known to include the Deicke K-bentonite (Kolata et al. 1996), making it partially correlative in time to the Decorah Shale. Redating of the Middle/Late Ordovician boundary may in fact put all four of these limestones into the Late Ordovician.

As the name indicates, the Camp Nelson Limestone was described from the area of Camp Nelson (Miller 1905); the type locality is a little to the south of the monument, around the area of the Kentucky River crossing. You can also find some nice faulting on the south side of the river (Andrews 2005). The Camp Nelson Limestone appears to be the oldest formation exposed in Kentucky. This was a bit surprising to me, and leads to the reflection that, thanks to accidents of geography and erosion, the bedrock at the surface in the entire state of Kentucky is younger than most of the bedrock exposed in Minnesota.

Hiding conulariids

I really hope to have a more complete update later, but suffice it to say that while tracking down references to a conulariid species from the Grand Canyon, I stumbled across George Winston Sinclair's 1948 thesis on conulariids. In this thesis there is a great deal of information about Minnesota's Ordovician conulariids that Sinclair did not publish in his lifetime, including several unpublished species. There is also the implication that at one time the University of Minnesota collections contained two-to-three-dozen conulariid specimens from the Glenwood Formation on up. This came as a surprise, because I did not recall having seen more than a half-dozen or so on my trips. Several possibilities presented themselves:
  • The conulariids were being kept separately from the other fossils when I visited, or were just somewhere I hadn't known to look;
  • The conulariids have been lost or stolen: if so, not much more can be added;
  • The conulariids passed into Sinclair's hands: this seemed worth following, because Sinclair built up a collection of conulariids and I knew that certain elements of the University of Minnesota collections had gone to others. For example, material from Berkey's Taylors Falls work was donated to the Smithsonian in recent years (Yochelson and Webers 2006).
I checked with folks at the University of Minnesota, University of Michigan Museum of Paleontology, and the Canadian Museum of Nature (the latter two institutions associated with Sinclair), but no luck to date. Hopefully this all works out in the wash. By way of apology, here's a photo of the type specimen of Ctenoconularia obex, one of the few Minnesota species Sinclair ended up publishing.

UMPC 6608, holotype of the conulariid Ctenoconularia obex, from the "Sprechs Ferry" (=lower Decorah) of Minneapolis.

One other conulariid note:
It turned out that one of the other conulariids Sinclair named came from the St. Peter Sandstone of Minnesota: Climacoconus humilis, described in Sinclair (1942) and promptly forgotten by virtually the entire universe (it's based on Carnegie Museum 4753 from Faribault, by the way). Maybe it's just my myopia showing, but it doesn't seem right that it's made almost no impression in the literature, even to be refuted. We are, after all, dealing not only with the St. Peter Sandstone, famous for having practically no body fossils, but also an uncommon and distinctive type of fossil!

Dystactophycus revisited

Back in July 2016, I showed a photo of a strange rock with concentric rings, which provided an excuse to riff on Dystactophycus, a possible trace fossil of a swirling crinoid. At the time, I thought it was unlikely that the photographed rock was Dystactophycus, or indeed of organic origin at all. A few months ago, the collector confirmed my general suspicions: he told me that mutual acquaintances have identified it as a modern fracture pattern, consistent with his later observations of features produced by air hammers punching into the Platteville.

References

Andrews, W. M., Jr. 2005. Geology and the Civil War in central Kentucky: Camp Nelson. Field Trip Guidebook, American Institute of Professional Geologists 42nd Annual Meeting.

Kolata, D. R., W. D. Huff, and S. M. Bergström. 1996. Ordovician K-bentonites of eastern North America. Geological Society of America, Boulder, Colorado. Special Paper 313.

Miller, A. M. 1905. The lead and zinc bearing rocks of central Kentucky, with notes on the mineral veins. Kentucky Geological Survey, Lexington, Kentucky. Bulletin 2.

Sinclair, G. W. 1942. The Chazy Conularia and their congeners. Annals of the Carnegie Museum 29(10):219–240.

Sinclair, G. W. 1948. The biology of the Conularida. PhD Thesis. McGill University, Montreal.

Wolcott, D. E. 1969. Geologic map of the Little Hickman Quadrangle, central Kentucky. U.S. Geological Survey, Washington, D.C. Geologic Quadrangle Map 792. Scale 1:24,000.

Yochelson, E. L., and G. F. Webers. 2006. A restudy of the Late Cambrian molluscan fauna of Berkey (1898) from Taylors Falls, Minnesota. Minnesota Geological Survey, St. Paul, Minnesota. Report of Investigations 64.

Sunday, December 2, 2018

Photos from Albuquerque

Back in October I attended the annual meeting of the Society of Vertebrate Paleontology, held at Albuquerque, New Mexico. The meeting was co-hosted by the New Mexico Museum of Natural History and Science. Part of the program of the annual meeting is a reception at a co-hosting institution, where the attendees can mingle among the institution's exhibits. I was fortunate enough to be in the company of JP and Sarah Hodnett, who are very familiar with the museum. (In fact, we'd actually spent most of that day there already, working the National Fossil Day event.) Thanks also to JP and Sarah for helping me get around Albuquerque!

We also had the able assistance of ceratopsids for National Fossil Day.

Sunday, November 25, 2018

Your Friends The Titanosaurs, part 6: Austroposeidon, titanosaurs of Balochistan, and Baotianmansaurus

For Thanksgiving (US), we're getting overstuffed with extra titanosaurs. We're also venturing to three different Cretaceous landmasses: South America for Austroposeidon magnificus, the formerly separate landmass of the Indian Plate for a group of titanosaurs from Pakistan, and Asia for Baotianmansaurus henanensis.

Sunday, November 18, 2018

Decorah gastropods (and some things that look like gastropods)

The snails* of the Decorah Shale are a lesser component of the fauna than bryozoans, brachiopods, or crinoids. My personal experience is that snails are uncommon except for certain beds, which feature abundant and diverse snails. One of these beds is perhaps 20 ft (6 m) above the top of the Carimona in St. Paul; this bed produced the plate in the "Equatorial Minnesota" box near the top of the page. For whatever reason, this bed also hosts abundant trilobite pieces, particularly of Eomonorachus. There's probably a facies thing going on, such that the original depositional environment was favorable to snails and trilobites; it's not quite as stark as, say, McKee (1938)'s mollusk and open marine facies of the Kaibab Formation (the very durable rock at the top of the Grand Canyon stack), but there's certainly some kind of difference. It might be a carbonate thing; both the underlying Platteville and overlying Cummingsville/Prosser, which have more limestone and dolomite, also have more diverse mollusks than the muddy Decorah (Sloan and Webers 1987). On the other hand, the relatively limited diversity and abundance of snails, combined with most genera having visually distinctive appearances, make it possible to summarize them in a reasonably brief guide.

*and things that look a whole lot like snails, and things that people argue about, such as Sinuites

Several snails in a small section of a slab: C for Clathrospira, S for Sinuites, and L for "lophospiroid".

Sunday, November 11, 2018

Rebbachisauridae

Diplodocoidea contains three wings: Diplodocidae, where the popular diplodocoids such as Apatosaurus, Barosaurus, Brontosaurus, and Diplodocus hang out; Dicraeosauridae, somewhat undersized and short-necked sauropods that are seemingly content to be represented in the public eye by Amargasaurus and its magnificently strange vertebrae; and Rebbachisauridae, also generally known for undersized and short-necked sauropods represented in the public eye by one exceptional taxon. In the case of rebbachisaurids, it's Nigersaurus, famous for its skull, which looks kind of like the animal habitually slept with its snout pressed against a wall.

Yeah, like that. Photo taken at a traveling exhibit at the Science Museum of Minnesota back in May 2014.

Sunday, November 4, 2018

Cumberland Bone Cave

There are a handful of notable Pleistocene "bone caves" in the Mid-Atlantic states. We've stopped at one of the classic sites already, Port Kennedy Bone Cave. Another classic site is Cumberland Bone Cave in western Maryland. Its scientific history began a few decades later than Port Kennedy, but both sites are of Irvingtonian age (between approximately 1.9 and 0.25 Ma), rather than a younger age like most Pleistocene sites, and the faunas from the two sites are often mentioned together.

Sunday, October 28, 2018

Your Friends The Titanosaurs, part 5: Argyrosaurus, Atacamatitan, and Atsinganosaurus

We're almost beyond the letter "A" in the alphabet of titanosaurs (for whatever reason titanosaur researchers have given a disproportionate number of genera names that begin with "A"). For this entry we have a historic name (Argyrosaurus superbus), the first non-avian dinosaur named from Chile (Atacamatitan chilensis), and our second well-represented smallish titanosaur from from western Europe (Atsinganosaurus velauciensis).