Saturday, December 31, 2016

2016 in Review

And so we close 2016, having gone from Death Valley, to Chickasaw National Recreation Area, to Fort Union Trading Post, to Interstate State Park, and back home. We contemplated paracrinoids, waded through 19th century shenanigans, got locked in a hadrosaur, withstood earthquakes and volcanoes, and were swarmed with crocodiles. (And occasionally I filled space with a random dinosaur or some photos.)

And in honor of that, an interesting triangular fossil in Platteville building stone on the St. Paul campus of the U of M. A hyolith?

Sunday, December 18, 2016

Club Late Ordovician

As I write this, it is about 10 degrees F below zero, with a windchill about 20 below. It's a good time to think about warmer things, like, well, equatorial Minnesota. When I work with the paleontology of the National Park Service, one thing I like to do is to compare fossil records across different parks. Several years ago, we combed through our various records and compiled a sort of database (okay, it's functionally almost nothing like a database, but that's the simplest way to describe it) on NPS paleontology. This compilation is such that now we can say, "Give us a rundown on all of our records for Middle Triassic park fossils," and the computer will do nothing because it isn't programmed to respond to verbal commands, but you can rest assured that we can very quickly find that information. It is therefore simple for me to pick out, say, the Late Ordovician records and make some thumbnail observations. I can thus present to you the exclusive Club Late Ordovician, as shown in the following map. (I could have called it Club Upper Ordovician, but it just didn't have the same ring.)

One of my famous giant captions. 1. Death Valley National Park (DEVA), California–Nevada; 2. Great Basin National Park (GRBA), Nevada; 3. Yellowstone National Park (YELL), Idaho–Montana–Wyoming; 4. Grand Teton National Park (GRTE), Wyoming; 5. Bighorn Canyon National Recreation Area (BICA), Montana–Wyoming; 6. Big Bend National Park (BIBE), Texas; 7. Chickasaw National Recreation Area (CHIC), Oklahoma; 8. Mississippi National River and Recreation Area (MISS), Minnesota; 9. Pictured Rocks National Lakeshore (PIRO), Michigan; 10. Effigy Mounds National Monument (EFMO), Iowa; 11. Buffalo National River (BUFF), Arkansas; 12. Hot Springs National Park (HOSP), Arkansas; 13. Stones River National Battlefield (STRI), Tennessee; 14. Natchez Trace Parkway (NATR), Alabama–Mississippi–Tennessee; 15. Katahdin Woods & Waters National Monument (KAWW), Maine; 16. Saratoga National Historical Park (SARA), New York; 17. Delaware Water Gap National Recreation Area (DEWA), New Jersey–Pennsylvania; 18. Chesapeake and Ohio Canal National Historical Park (CHOH), Maryland–Virginia–West Virginia; 19. Denali National Park & Preserve (DENA), Alaska. The gray blob over much of the eastern half of the US is the distribution of Late Ordovician bentonite beds as per Kolata et al. 1996 (also the source for the discussion of correlations below); the beds may also go somewhat farther to the west in the subsurface.

Sunday, December 11, 2016

Fossil Crocs of the Science Museum

Although the dinosaurs get the most press, the Science Museum of Minnesota's paleontology department has a strongly diversified portfolio of ancient reptiles. In particular, champsosaurs and crocodyliforms (modern crocodilians and their closest extinct relatives) are well-represented in the collections and on exhibit. The Science Museum features mounts of four fossil crocs, each one filling different places in their ecosystems: an apex terrestrial/freshwater croc (Borealosuchus formidabilis), a large estuarine croc with elongate jaws living alongside whales (Gavialosuchus carolinensis), a medium-sized terrestrial/freshwater croc from a dinosaur-dominated setting ("Goniopholis"), and a house-pet-sized terrestrial/freshwater generalist (Wannaganosuchus brachymanus). This diversity shouldn't be too surprising. Crocodylomorphs, with around 225 million years of time on their hands, have done quite a bit of experimentation, including truly marine thalattosuchians and small, terrestrial, occasionally dinosaur-like "sphenosuchians".

Sunday, December 4, 2016


For a small herbivorous dinosaur with no crest, horns, etc., Thescelosaurus has managed to sweep through a respectable number of species. There's the type species (T. neglectus), T. assiniboiensis, T. edmontonensis, T. garbanii, Bugenasaura infernalis, and the subject of today's entry, which entered science as Thescelosaurus warreni but which is better known as Parksosaurus (warreni or warrenae, depending on how you feel about far-after-the-fact emendations).

Saturday, November 26, 2016

Cottage Grove Ravine Regional Park: the green rocks of home

I come from Cottage Grove, Minnesota, and in the southeast part of town there's Cottage Grove Ravine Regional Park. Up until a few weeks ago, I had no idea that there was actually exposed bedrock in the park. The only outcrops I knew of in town were a couple of pockets around the compost site, a couple of spots in Old Cottage Grove, and some outcrops of the St. Peter Sandstone up high on Camel's Hump overlooking Highway 61 (there's a little park up on the crest of the hill now, with a good view across the valley, by the way). Obviously, I had to have a look around.

The rocks, counterintuitively, are the green things in this photo.

Sunday, November 20, 2016

Meanwhile, over at the Science Museum

Recently, the Science Museum of Minnesota reconfigured the exhibit space for the paleontology in conjunction with changes to other parts of the floorplan. I don't recall if the previous configuration had been stable all the way back to the 2005 Society of Vertebrate Paleontology meeting (I do know a nice Goniopholis was added around 2010), but where once it had looked like this:

January 2013; watch the space on the left of the Stegosaurus.

Now it looks like this:

That Triceratops wasn't there before...

Two major components, the Morrison dinosaurs and the Wannagan Creek fossils, are still where they had been. The major differences are in the section on the east, with the removal of some visible lab space and some more portable specimens, most notably a sort of "circus ring" of small- to medium-sized Cenozoic animals, mostly mammals.

And a tortoise.
In their place are a group of mounts from the Oligocene of coastal South Carolina (transferred from the floor above) and the well-known Science Museum Triceratops, relocated from another part of the floor. A Triceratops going mobile is just not a common occurrence these days, so naturally the event received some local coverage. A few other pieces were also rearranged, including the Xiphactinus lurking behind the Stegosaurus in the first picture above, some of the remaining mammals, the Goniopholis, and your friend and mine Thescelosaurus. Green River Formation fossils also get more prominence.

Triceratops (who also answers to "Fafner") plus overhead pterosaur pal in foreground. The South Carolina mounts are visible in the background by the neon; you can see a whale, pseudodontorn,and sea turtle in the air above the hind end of a mostly obscured croc (next photo).

Estuarine croc Gavialosuchus (or Thecachampsa) carolinensis has an honest face. I was glad that space was made for the South Carolina mounts; many places have Morrison dinosaurs, but you can't see Wannagan Creek and South Carolina fossils just anywhere.

On the one hand, the Triceratops no longer has its niche with the backdrop:

On the other hand, you can now walk around the whole mount, if for example you should want to look at the legs and hips:

Like this, perhaps.

I may cover some of these exhibits in a bit more detail in the coming weeks, given the approaching busy holidays. Till then, though, Allosaurus bids you all adieu:

Sunday, November 13, 2016

Some thoughts on St. Anthony Falls

If you're familiar with the history of Minneapolis, you probably know that beneath what we now call St. Anthony Falls are the remains of the natural St. Anthony Falls. The real falls went kaput quite a while ago; October 5, 1869, to be precise. The creation of the Hennepin Island tunnel is usually named as the culprit, but after seeing this photo I am beginning to suspect suicide. For various reasons, the presence of a waterfall or a reasonable facsimile thereof was required, so with the aid of the Army Corps of Engineers, the body was embalmed in wood and cement, and propped up in its accustomed place.

Granted, it's a pretty darn good job of embalming.

Sunday, November 6, 2016


Out of the blue, my supervisor recently asked me if I knew anything about a piece of art depicting a shall-we-say stylized and retro dinosaur labeled "Claosaurus" at the Berlin Aquarium. This was one of those odd coincidences that we are taught to avoid in fiction: I'd been thinking about writing a post on Claosaurus, and now I was being commanded by the gods of serendipity. I've had a soft spot for this modestly publicized duckbill since before I was ten, when I read about it in a magazine and it became my first "hipster" dinosaur. (My second was Epanterias, because this was the late '80s/early '90s, when iconoclasts like Bob Bakker and Greg Paul had just raised the siren song for the splitting of Allosaurus fragilis and the community was not yet hardened by cynicism about mysterious giant theropods not known from enough material to draw a dirty look in the express checkout.)

Sunday, October 30, 2016


The Triassic was an experimental time for large tetrapods. The Permian–Triassic extinction event had eviscerated the prevailing communities of diverse therapsids (relatives of mammals), various early reptiles, and large temnospondyl amphibians (for more on them, Tetrapod Zoology has made them a cottage industry since 2007). Into that vacuum the survivors seem to have gone with the strategy of "throw everything at the wall and see what sticks". Some lineages stuck quite well. Early turtles and sphenodonts (tuatara) showed up during the Triassic, as well as forerunners of crocodilians and mammals. Lizards are probably in there too somewhere. Frogs may predate the Triassic, but the first good fossils are Triassic. Famously, the dinosaur line, which eventually produced birds, appeared in the Triassic as well. Long-lived but now extinct groups that got their start in the Triassic include the ichthyosaurs, plesiosaurs, pterosaurs, and our friends the choristoderes. There was also a veritable heap of briefly successful groups that for whatever reason went extinct by the close of the Triassic. Among them: aetosaurs (armored herbivores that look vaguely like ankylosaurs), drepanosaurs, nothosaurs and other plesiosaur cousins, placodonts, phytosaurs (crocodiles before there were crocodiles), rauisuchians (carnivores with theropod-like skulls), rhynchosaurs (big beaked herbivores), tanystropheids (necks plus neck delivery systems), thallatosaurs (lanky marine reptiles), and all kinds of other strange one-hit wonders.

Until the 1960s, dinosaurs seemed to have more or less just appeared in the Late Triassic, with theropods and prosauropods (in the sense of "all them sauropodomorphs what ain't sauropods")  recognized as present. What came before those theropods and prosauropods wasn't known, although there were a few guesses and extrapolations. One popular option of the time was that, technically speaking, there weren't really any basal dinosaurs because "dinosaurs" themselves were an artificial group "united" by some coincidental bits of anatomy related to being large land-living animals. This view is practically extinct, although I cannot say completely extinct. One of the great truths of humanity is that there is someone who will believe any proposition. One of the great truths of the Internet is that now you can find that person (or oftentimes, they will find you, if you are holding an opposing position). Other researchers drafted in various poorly known Triassic reptiles. The most enduring may have been Teratosaurus, which people who got into dinosaurs before the late 1980s will probably remember as a sort of megalosaur-like thing stalking the wilds of Late Triassic Europe. It was actually based on jaw material from a rauisuchian, with prosauropod skeletal remains misattributed to it. The misidentification of Teratosaurus, though illustrative, serves mostly as a lesson in the honesty of bonebeds. More recent work with Reveultosaurus, Shuvosaurus, and others shows that it can be darn hard to separate true early dinosaurs from the various wacky archosaurs of the Triassic if you've only got a few remains. The terrestrial Triassic still has more fools to make.

Of all the various bits and pieces put forward as early dinosaurs in the days before the 1960s, the only one that actually is both vaguely useful and does not easily slot into any of the known clades of true dinosaurs is Saltopus elginensis, described in 1910 by von Huene. It got to be in all the best dinosaur books as an archetype, overcoming the significant handicap of being a terrible specimen, which just goes to show that sometimes all you have to do to succeed is show up. The first useful basal dinosaurs to be described, Herrerasaurus and Ischisaurus, were described in 1963, followed by Staurikosaurus in 1970. They were followed by Lagosuchus, Lagerpeton, and Lewisuchus in 1971 and 1972, which were underappreciated at the time but eventually were shown to be dinosaurian cousins once we got that whole "unnatural Dinosauria" thing worked out of the collective scientific system. At the present, there are around 20 species of near-dinosaurs, from Dinosauromorpha to Dinosauria. This doesn't compete with, say, Titanosauria, but it's not bad for about 45 years of serious work. There's a little wiggle room built in depending on how charitable you feel toward Pseudolagosuchus, how you handle "Thecodontosaurus" alophos and borderline cases (e.g. Agnosphitys, Alwalkeria, Teyuwasu), and the occasional analysis that pulls Herrerasauridae or Eoraptor out of Saurischia. Some of them can be grouped as lagerpetids, diminutive bipeds, or as silesaurids, larger animals which could reach roughly the size and shape of Fred Flintstone's pet Dino. At least one of these, the namesake Silesaurus, was equipped with a little can-opener of bone at the tip of its lower jaw, perfect for being confused with the ornithischian predentary. A few others either don't slot comfortably into either group, or are poorly known (and I tend to the conservative when it comes to where I slot, which in this case mostly affects Lewisuchus/Pseudolagosuchus). The chart below lays them out with age and continent denoted. One thing to note is the abundance of species for South America and Africa, which not only suggests a Gondwanan origin but also provides a partial explanation for why these animals have only come to light in the past few decades: there haven't been a lot of paleontologists in those areas until recently.

Click for further enlightenment

Another important thing to keep in mind is to avoid the trap of turning extinction and evolution into a morality play. "Near-dinosaurs" were not merely a sideline, or waiting hopefully to eventually evolve into dinosaurs, or a bunch of saps that got pushed out of the way by their cousins. They were their own creatures, diversifing into several lineages and living alongside their more famous cousins for twenty or so million years, at least. We currently have named examples from four continental landmasses, and it would hardly be surprising to add a few more landmasses, five to ten million years, or additional lineages.

Dromomerom romeri, by Nobu Tamura (from For whatever reason I've always found this restoration charming.

Sunday, October 16, 2016

Year One of The Compact Thescelosaurus (now with extra choristoderes)

Mid-October is the time of National Fossil Day, as well as just past the anniversary date of the late lamented Thescelosaurus! and the introduction of The Compact Thescelosaurus. In honor of the occasion, I've made a couple of additions. One is a new page with a selection of online museum collections databases. The other is a new worksheet on The Compact Thescelosaurus, featuring choristoderes. This sheet is the first of what I hope to be a series covering other fossil groups; choristoderes were selected for the honor this time around because there are only a few. I have a few candidates in mind for the next addition, perhaps a year from now; it depends on how ambitious I'm feeling. I haven't given up on the idea of making a version of the old website's contents available, but I haven't really decided how to do it.

So it's not really surprising that I came up with a post on subtle nuances of the nomenclature of Champsosaurus.

Sunday, October 9, 2016

The Platteville Formation revisited

For the person interested in fossils in the Twin Cities, the Decorah Shale is money in the bank. It's a cooking pot that never empties, a gas tank that's always full. If you have a patch of it, you cannot lose. The Platteville Formation is more like a lottery ticket. If you pick up a random piece, the chances are good it will have nothing, or maybe an imperfect brachiopod mold or two, or some "eyelashes" from shells in cross-section, or half of a burrow. Even when you do find a chunk that's loaded with fossils, usually it's 95% brachiopods and 5% snails, with a couple of crinoid columnals, bivalves, or bryozoans for variety. Every so often, though, you will come up with something unusual. It's true that the Decorah also rewards in-depth exploration, but the "floor" of discovery is so much higher in the Decorah that the feeling when you do find something out of the ordinary in the Platteville is much different. It's more of an accomplishment. The universe has rewarded your perseverance, has conspired with taphonomy, lithification, and erosion to put someone with the proper skills and inclination (i.e. you) in this place at this time to observe and appreciate this fossil. (I will refrain from pulling out the conulariid again.)

I've seen a few of these big snails; not sure about the genus yet.

In terms of preservation, the Decorah Shale is a strictly representational artist dedicated to faithful reproduction of the fossils, thanks to relatively mild conditions for fossilization and diagenesis (the stuff that happens during and after the formation of sedimentary rocks, like replacement of calcite with dolomite). Thanks to dolomitization, the Platteville Formation of the Twin Cities Basin is a sort of minimalist impressionist, retaining only some essential essence of a given fossil while losing most of the fine details. (It also has a thing for sparkles, what with all of the fine dolomite crystals.)

And then we've got blocks like these, doing a decent job of imitating the Decorah. I think I can place the source to a specific bed in the upper Mifflin, but it may be very localized.

On Saturday, I was the guest paleontologist for the Second Saturday fossil event at Coldwater Spring. (I'm the tall one with the facial hair.) After having spent a lot of time along the gorge, I think it is fair to say that Coldwater Spring is one of the best places in the Twin Cities to be in close contact with the Platteville Formation, if not the best. It is certainly the best place to take people of all ages and experience levels to see Platteville rocks and fossils. In most locations on the gorge, the Platteville is a brooding presence capping whitish bluffs of St. Peter Sandstone, inaccessible to all but the most reckless. At some places where a ravine joins the gorge, such as Shadow Falls, Minnehaha Falls, and a few locations on the Minneapolis side of the river, you can walk around parts of the Platteville, but you also are stuck on narrow paths where you've got the Platteville on at least one side, sometimes two (the other side is the one above your head), and the steep slope of the bluffs on the other. This can be chancy when you're on your own and is not feasible for groups of non-professionals, and even when you do go, you usually only get to see the lower part of the formation. By virtue of erosion and some human modification, Coldwater Spring allows you to appreciate the Platteville at close range on level ground. The gentle slope of the bike path trail means it's a short walk from the lower Platteville exposed at the south end of the park to the upper Platteville at the north end. This chance alignment also means you can get right next to the contact with the Glenwood at more or less level ground as well. October is also one of the best times to visit: the vegetation is dying back so you can see the rocks, the temperature and humidity are comfortable, mosquitoes and ticks are in retreat, and the ground is is not saturated with spring snowmelt.

The park is also great for these fossil walks because of the fossiliferous building stone and the presence of several areas with lots of small eroded blocks of the Platteville. I can bring families to the building stone used in the parking area and near the Spring House to give them an idea of what the fossils look like, and then the kids can rummage around in the loose stone. It's a great time: if your family is here, you're probably already the kind of kid who likes to rummage around in rocks; the Platteville is a reliable producer of shelly fossils, so everybody should get to see something; there's that paleontologist guy who can tell you what you've found, and if it's really interesting he'll call everybody over to see what it is; and there are also lots of interesting bugs and spiders and so forth if you're striking out on the fossil front, without anything too dangerous (one of the perks of exploring in Minnesota, although we do scare the bejeezus out of many innocent pillbugs). I get lots of questions, and nobody seems to mind that it's "catch and release" here (NPS property). I've been around the rock pile a few times, so I'm jaded. It takes more than a couple of brachiopod molds to get my interest. But if this is your first time to visit fossils in the field, to turn over a rock and maybe be the first person to ever see the brachs on that particular slab, you can't do much better.

First shells!

Sunday, October 2, 2016

Fossil type specimens of the National Parks

I've just returned from the 2016 Geological Society of America annual meeting at Denver, wherein I gave a presentation on our recently updated inventory of paleontological resources in the Mojave Desert Inventory and Monitoring Network. Trying to stuff Death Valley National Park, Great Basin National Park, Lake Mead National Recreation Area, Tule Springs Fossil Beds National Monument, and friends into a sub-15-minute box is an interesting experience. I could have done a semester-long class and still missed some things.

Why, it's a giant blue bear. You don't see that every day, unless of course you live in Denver. It lost its name tag, so they won't let it in.

Sunday, September 18, 2016

Sunday nautiloids

An interesting fact concerning nautiloids and the Platteville Formation is that the biggest nautiloid shells are often found only partially preserved, because their diameters (up to around 10 in/25 cm) exceeded the depth of the Platteville ooze they sunk into (Webers 1972a, 1972b). This means that when you see a fossil of one of these big Platteville nautiloids where the cross-section is partly round and partly irregular, you can guess that the round part represents what was buried; the rest of it was eroded off. So, while a small nautiloid can be completely buried:

...the big guys aren't so lucky. Take these examples from Sogn, Minnesota:

The more impressive of the two, featuring the part that looks like a nautiloid.

The cross-section of this specimen. Round was down (in the mud), originally.

The cross-section of the other, less impressive nautiloid.

Half a nautiloid is better than none, and for these two nautiloids, it permits a bonus: other shells and organic fragments collected in the eroded nautiloids. Notice the off-white patch near the center of the first cross-section above? Here's a close-up:

This is a small lingulid brachiopod (modern cousin Lingula; see a larger relative from Oklahoma rocks of reasonably similar age to the Platteville here). There are several fossils larger than millimeter-sized chips visible on these nautiloids, and they all appear to be the same kind of lingulids. This is an interesting association, but I couldn't tell you what it means. Here are two of the better-preserved examples:


Webers, G. F. 1972a. Paleoecology of the Cambrian and Ordovician strata of Minnesota. Pages 474–484 in P. K. Sims and G. B. Morey, editors. Geology of Minnesota: a centennial volume. Minnesota Geological Survey, St. Paul, Minnesota.

Webers, G. F. 1972b. Paleoecology of the Ordovician strata of southeastern Minnesota. Pages 25–41 in G. F. Webers and G. S. Austin, editors. Field trip guidebook for Paleozoic and Mesozoic rocks of southeastern Minnesota. Minnesota Geological Survey, St. Paul, Minnesota. Guidebook 4.

Sunday, September 11, 2016

Port Kennedy Bone Cave supplement

The National Fossil Day monthly feature for September is Port Kennedy Bone Cave (archival link here; added 2017-03-27), in Valley Forge National Historical Park. There is a Pleistocene theme this year, and caves are great for Pleistocene fossils. Port Kennedy Cave is the second cave-based feature I've written this year, after Rampart Cave, and the third cave feature total (we've also got Gypsum Cave). We've still got three months to go, and I could certainly see some more caves in there. Anyway, I'm writing this to direct you to a story on an unusual site (you get middle Pleistocene mammals, Edward Drinker Cope, Valley Forge, a rumored buried train, and bone preservation compared to "over-ripe pears"), and provide some supplementary material on the species described from the fissure.

Monday, September 5, 2016

Regarding Liaoningosaurus

By now you may have heard about the new paper by Ji Q. et al. on Liaoningosaurus, proposing some surprising things about the paleobiology of this ankylosaur. Andrea Cau already had a go at it over at Theropoda. I'm afraid I won't be as concise or insightful, but possible gut contents are involved, and having fought my own gut-content dinosaur to a truce, I think I can bring a distinct perspective to this paper. 

Wednesday, August 31, 2016

The Great Minnesota Brachiopod Caper of 1892

I've been looking to write something on Frederick Sardeson for a little while now, but Weiss (2000) has taken care of his biography in great detail, and there's enough going on there that to summarize it would still give you a long, long post. Instead, as I was working this particular incident stood out and volunteered to serve as a microcosm of his career. I present the Great Minnesota Brachiopod Caper of 1892. Weiss (1997) also got there before me, but this is a much more compact bite to take.

First, our cast of characters as they were in 1891–1892:
Christopher Hall, the head of the University of Minnesota's Department of Geology;
Frederick William Sardeson, former law student turned geology graduate student under Hall;
Charles Schuchert and Edward Oscar Ulrich, up-and-coming geologists/paleontologists out of Cincinnati; and
Newton Horace Winchell, the head of the Minnesota Geological and Natural History Survey.

And the situation:
Winchell was not a paleontologist, but he had a lot of fossils. In order to deal with them, he assembled a group of paleo-hotshots. For our purposes, the most significant are Schuchert, a budding brachiopod expert, and Ulrich, who could deal with a wide range of fossil groups. They'd already worked together on projects for the surveys of other states, so were experienced in this line of work. Winchell's team described hundreds of fossil species, with the culmination of their work being the great multi-volume "Geology of Minnesota" series. It is the creation of this series that led to Sardeson getting bluffed out of six brachiopod species by Ulrich and Winchell. For brevity, let us describe the events like this:

  1. Winchell brings in Schuchert to describe the numerous brachiopods.
  2. Hall directs Sardeson to bring Schuchert up to speed on the local brachs. Hall had previously worked with Winchell on the survey and dislikes him, although he is generous enough in this case.
  3. Sardeson and Schuchert have an informal deal that Sardeson will not publish any new brachiopod taxa until Schuchert has his work out.
  4. The "Geology of Minnesota" series is taking a long time to complete. The draft of the brachiopod chapter (Winchell and Schuchert 1895) is pretty much ready to go by late March of 1892, though, and Schuchert leaves town. In the meantime, Sardeson has nearly completed his graduate work, and has prepared a joint publication with Hall on the local Paleozoic rocks. An essential part of this is Sardeson's biostratigraphy, which incorporates a number of undescribed taxa. Hall insists that descriptions be published in advance of the joint paper.
  5. Ulrich finds out that Sardeson is preparing descriptions of new species, including brachiopods, which he promised not to do per point 3. This manuscript will be ready to go by early April. Winchell is not pleased by this turn of events.
  6. Winchell and Ulrich opt to extract part of the manuscript prepared by Schuchert to preempt Sardeson. It just so happens that the Winchell family owns a journal and Winchell himself is the editor (The American Geologist, which later kind of turns into The Pan-American Geologist). This is convenient. However, Sardeson's descriptive work, coincidentally enough due to be published in a journal edited by Hall (Bulletin of the Minnesota Academy of Natural Sciences), is almost ready for publication. There isn't enough time for Winchell and co. to preserve priority, or is there?
  7. Fittingly enough, on April 1, 1892, Ulrich provides Sardeson with a fake preprint of the extracted article, bluffing that it has already been mailed out. This has not happened, and in fact only two copies of the April 1 preprint are known to exist: Sardeson's copy and a copy kept by Ulrich.
  8. Sardeson's own article is mailed out April 6.
  9. An actual preprint of Winchell's article is mailed out April 21, with a note on the title page that it was first distributed April 1, 1892. The note does not explain that the distribution consisted of the single copy supplied to Sardeson.

The immediate result is that perfidy is rewarded, at least as far as Sardeson is concerned; the community takes it at face value that the April 1, 1892 date on the Winchell and Schuchert article is legit. Sardeson is "scooped" on six brachiopods: Orthis minnesotensis, taken by Winchell and Schuchert's Orthis meedsi; Orthis petrae, taken by Orthis proavita; Rhynchonella sancta, taken by Rhynchotrema inaequivalis var. laticostata; Streptorhynchus subsulcatum, taken by Strophomena scofieldi; Strophomena halli, taken by Leptaena charlottae; and Zygospira aquila, taken by Hallina nicolleti. The episode does not reflect well on any of the participants: Hall forced Sardeson into the mess, Sardeson broke his word to Schuchert, and Winchell, Ulrich, and to a lesser extent Schuchert came up with a new twist on the time-honored game of "screw over the grad student". For good measure, Winchell's team also appropriated the framework of Sardeson's biostratigraphic zones without giving him much credit. In the long run, the episode blows over as another quaint example of academic hardball. Hall is more or less forgotten today. Schuchert works with the U.S. Geological Survey and the National Museum of Natural History before moving on to Yale for the long term, where he becomes the god of brachiopods and eventually makes up with Sardeson. Ulrich goes on to the USGS, where he continues working on the lower Paleozoic and unsuccessfully proposes two additional periods out of the Cambrian and Ordovician (the Ozarkian and Canadian). Winchell successfully guides the Survey work to completion, retires to archeology, gets a number of things named after him, and is now more or less the only geologist based out of Minnesota that anyone has ever heard of. Sardeson embarks on a tempestuous career.

Sardeson was the one left holding the bag, which becomes something of a pattern for him. He was a fascinating paleontologist who combined aspects of 19th century heroic geology with brilliant insights on topics such as paleobiology, paleoecology, and biostratigraphy, along with very un-19th-century ideas on when to name new species. Over several decades he amassed a collection of thousands of fossils from the Ordovician of Minnesota, carefully plotted stratigraphically. Unfortunately, for all of his gifts, he also had an uncanny knack for marginalizing himself through sarcasm, paranoia, and professional contempt. (I'm not going to get into chicken-and-egg, but the events of 1892 probably did not increase his trust in others.) He quarreled with most of the geologists he encountered and entered into several long-running feuds which, despite whatever justification, did him more harm than good. He came up with the earliest name for what we now call the Platteville Formation and Decorah Shale (Beloit Formation, 1896), but was ignored in favor of the Platteville Formation, coined years later by a USGS geologist (Bain 1905). He was prevented from working on the geology of the St. Croix Valley by Ulrich and Charles Walcott (not counting the fact that Sardeson and Ulrich were not exactly buddies, Ulrich had staked out that area as part of his turf, and Walcott was wary of anyone who might show him up in his Cambrian sections, and Sardeson did not mind showing people up). He was dismissed from the University of Minnesota in 1913 and ended up blacklisted from all of the geology journals except the eccentric Pan-American Geologist. Through it all, he displayed superhuman perseverance. He was publishing up to 1940, into his 70s.


Bain, H. F. 1905. Zinc and lead deposits of northwestern Illinois. U.S. Geological Survey, Washington, D.C. Bulletin 246.

Sardeson, F. W. 1892. The range and distribution of the lower Silurian fauna of Minnesota with descriptions of some new species. Bulletin of the Minnesota Academy of Natural Sciences 3(3):326–343, 408–413.

Sardeson, F. W. 1896. The Galena and Maquoketa shales. Part 1. American Geologist 18:356–368.

Weiss, M. P. 1997. Falsifying priority of species names: a fraud of 1892. Earth Sciences History 16:21–32.

Weiss, M. P. 2000. Frederick William Sardeson, geologist 1866–1958. Minnesota Geological Survey, St. Paul, Minnesota. Bulletin 48.

Winchell, N. H., and C. Schuchert. 1892. Preliminary descriptions of new Brachiopoda from the Trenton and Hudson River groups of Minnesota. The American Geologist 9:285–294.

Winchell, N. H., and C. Schuchert. 1895. Sponges, graptolites, and corals from the Lower Silurian in Minnesota. Pages 55–95 in Lesquereux, L., C. Schuchert, A. Woodward, E. Ulrich, B. Thomas, and N. H. Winchell. The geology of Minnesota. Minnesota Geological and Natural History Survey, Final Report 3(1). Johnson, Smith & Harrison, state printers, Minneapolis, Minnesota.

Sunday, August 21, 2016

Champsosaurus: Adventures in 19th century taxonomy

It all started innocently enough with a couple of paragraphs in the 1870 Proceedings of the Academy of Natural Sciences, submitted on behalf of Joseph Leidy. The item notes that Leidy had received a reptilian vertebral centrum (the body of the vertebra, minus all the processes and such) collected by Ferdinand Vandeveer Hayden from the Moreau River, probably from Cretaceous rocks. It reminded Leidy of the vertebrae of marine reptiles, specifically Nothosaurus, so he proposed to name it Nothosaurops, type species N. occiduus. So far, so good. He got around to a longer description in 1873, in which he mostly repeated the 1870 information, but also included some figures of the fossil. Unfortunately, somebody goofed, because the text refers to something called Nothosaurus occiduus, but the plates and captions are using Nothosaurops occiduus. This would not be of much modern interest except for the fact that there is a good chance the specimen is the first described fossil of Champsosaurus.

Sunday, August 14, 2016

Fort Union Trading Post National Historic Site

About a week ago I returned from Fort Union Trading Post National Historic Site, where I'd been dispatched on official business. Fort Union Trading Post NHS, not to be confused with Fort Union National Monument in New Mexico, is located just north of the Missouri River on the North Dakota–Montana border. The reconstructed trading post itself is in North Dakota, but just barely; you can park in Montana and walk to it in less than five minutes (and gain an hour doing so, because you're also crossing time zones. Watch out for time paradoxes!). The fort was established for the American Fur Company in 1828 and lasted until 1867, after the fur boom years had passed. When people talk about forts in the American West, they often conjure images of cavalry, cattle, covered wagons, warfare with Native Americans, and so on. Fort Union, although it has appropriate prickly pears and yucca, was not a military post, although some of its building materials did become part of the Army's Fort Buford just down the river. Instead, as the name makes plain, it was a trading post, where Native Americans from many tribes traded furs for goods. At the time, it was ideally situated right above the Missouri River, but rivers get restless and this one has moved well south on its floodplain. Fort Union itself is not a hotspot for finding fossils, although an occasional inch-scale fragment of petrified wood can be seen, not an unusual thing for North Dakota (and if you do visit the fort and see such a piece, please don't take it!). However, the fort has a place in the historic development of North American paleontology.

Most of Fort Union from just outside the southwest bastion
This all goes back to a fortunate convergence of geography and company policy.  The AFC, via the Chouteau family, was noted for its support of artists and scientists, including such notables as John James Audubon, George Catlin, Joseph Nicollet, and Prince Maximilian of Weid, and encouraged their activities (Chaky 2015). Alexander Culbertson, the bourgeois (or manager) of Fort Union from 1837 to 1847, at times traveled from Fort Union to Fort John on the Laramie River, via Fort Pierre in what is now South Dakota. Fort John is better known as Fort Laramie, which incidentally also did not start out as an Army post, but as a fur trading post. It only became an Army post in 1849. The Fort Pierre–Fort John route took him across the Mauvaises Terres (spelled various ways in various sources), today better known as the White River Badlands. On these trips, he would occasionally collect fossils. He is probably the source of the first scientifically reported Badlands fossil, a jaw fragment which became named Paleotherium prouti and which is now known to have belonged to a brontothere (Wischmann 2000). He definitely provided the fossils that Joseph Leidy described as Poebrotherium wilsonii (a camel) and Merycoidodon culbertsonii (an oreodont, in fact "the" oreodont) (Chaky 2015), kick-starting vertebrate paleontology in the Badlands and west of the Mississippi in general. Early press on these finds in the late 1840s attracted other geologists. Among them was David Dale Owen, at that time working on a survey of Iowa, Minnesota, and Wisconsin. He dispatched subordinate John Evans to the Badlands in 1849. Evans returned with another load of vertebrate fossils which was sent to Leidy, whose descriptions of the bones makes up a chapter in Owen's massive 1852 survey publication. The AFC got into the act by sending Alexander's brother Thaddeus with another group in 1850 to make additional collections. In 1853 there was even an early foretaste of the Bone Wars when a government railroad survey crew including Evans butted heads with Ferdinand Vandeveer Hayden and Fielding Bradford Meek (Chaky 2015).

Another lasting trace of the early paleontological work in the area is the name of a rock unit that is commonly exposed in western North Dakota and eastern Montana: the Fort Union Group (North Dakota Geological Survey name) or Fort Union Formation (Montana Bureau of Mines and Geology name). This Paleocene-age sedimentary unit is the source of the Wannagan Creek fossils which can be viewed at the Science Museum of Minnesota, and makes the picturesque badlands of Theodore Roosevelt National Park and Little Missouri National Grassland. It does not appear to be exposed within Fort Union Trading Post NHS, although it is exposed in the uplands just beyond. Hayden used Fort Union as his base of operations in 1854 and early 1855, making collections of nonmarine mollusks from sites around the fort (Hartman 1999; Chaky 2015).

The Fort Union Group in the North Unit of Theodore Roosevelt NP


Chaky, D. 2015. Fossils and the fur trade: the Chouteaus as patrons of paleontology. We Proceeded On 41(2):12–23.

Hartman, J. H. 1999. Western exploration along the Missouri River and the first paleontological studies in the Williston Basin, North Dakota and Montana. Proceedings of the North Dakota Academy of Science 53:158–165.

Owen, D. D. 1852. Report of a geological survey of Wisconsin, Iowa, and Minnesota; and incidentally of a portion of Nebraska Territory. Lippincott, Grambo & Co., Philadelphia, PA. Available at (plates not included), (full plates) or

Wischmann, L. 2000. Frontier diplomats: Alexander Culbertson and Natoyist-Siksina' among the Blackfeet. University of Oklahoma Press, Norman, Oklahoma.

Sunday, July 31, 2016

(former) Ash beds in St. Paul

Although many Minnesotans are aware of the great Midcontinent Rift that runs across the state, it's less generally well-known that evidence of some of the largest known volcanic eruptions in the history of the planet can be found in the Twin Cities. In fact, you can easily put your hand on a layer of former volcanic ash by taking a short walk at our old friend Shadow Falls Park, at the end of Summit Avenue.

Sunday, July 24, 2016


Nothing particularly earth-shattering today. I would just like to direct you to the right-hand sidebar, where I've added a section to make it easier to get to The Compact Thescelosaurus, as well as a page that collects a few dozen sources for downloadable or viewable publications. As long as we're on the latter subject, I'll throw out a plug to Barnum Brown's description of the integument of the AMNH's panel-mounted Corythosaurus, and Henry Fairfield Osborn's description of the same for the "trachodon mummy" (note: 74 mb, but you also get an article on the skulls of Allosaurus and Tyrannosaurus). It also gives me an excuse to use this charmingly old-school restoration of various non-contemporaneous duckbills hanging out, found in Brown's publication.

Sunday, July 17, 2016

Hierosaurus sternbergii

One of the notable quirks of nodosaurids is a predilection for washing out to sea. Nodosaurus textilis and Stegopelta landerensis are a couple of featured examples. We turn now to another species from the Western Interior Seaway: Hierosaurus sternbergii.

Sunday, July 10, 2016

Dystactophycus, the crinoid swirl

A few weeks ago, a friend brought in an odd object to the Science Museum, which he had collected from an excavation in the vicinity. The object is a carbonate rock featuring concentric ridges that seem to be radial around a central depression. On the off-chance that it was some kind of exotic trace or trace-like pseudofossil, and that it had been illustrated, I went across the hall, pulled the volume of the Treatise on Invertebrate Paleontology that covers traces, and was pleasantly rewarded in the pseudofossil section with an illustration of something called Dystactophycus. The illustrated specimen was even from the Cincinnatian, which is practically as good as the Platteville/Decorah, being just a couple of million years younger. Of course, when something comes this quickly I'm honor-bound to be suspicious, but in this case the actual existence of something like Dystactophycus is more interesting than the question of whether or not I was right. (I do get back to the question of identity in the last paragraph.)

Dystactophycus, as currently understood, is one of those things that makes perfect sense once you've heard of it, but otherwise would probably never occur to you. It is composed of concentric markings on a conical structure. The initial describers (Miller and Dyer 1878) interpreted it as a seaweed, because the year was 1878 and the campaign to wrap peoples' minds around invertebrate trace fossils was far from being over. In short order, it was dismissed as an impression of a concentrically ringed bryozoan (Monticulipora by way of Lichenalia concentrica, both then considered corals) (James 1885, 1895–1896). More recently, Dystactophycus has been attributed to crinoids (Osgood 1970; Meyer and Davis 2009). As Osgood described it, the earlier researchers had the thing upside down: instead of an upward-pointing cone, the center was a low depression. The stem was partially buried by mud and the rest of it was spun around by swirling currents, causing its arms to sweep out an area that became the depression and quite naturally leave concentric markings. At some point, the crinoid detached, and the depression filled in the absence of the sweeping action. Although kind of like a trace fossil, these markings are not trace fossils because they are not evidence of biological activity. Think of them more like an Ordovician equivalent to marks left by a log on a river bottom (tool marks, in the parlance). (If you'd like to see a true crinoid trace, check this out!)

The specimen in question (I didn't have a scale handy, so my fingertips will have to do). Although similar in some ways to Dystactophycus, I don't think it's an example.

So, do I think that the specimen in hand is an example of Dystactophycus? Although it is superficially similar to the description, there are a couple of characteristics that lead me to say "no". The major issue is that the specimen is not a simple cone shape. Instead, after rising from the center, it slopes again (so kind of a doughnut shape), and the concentric lines are not confined to the cone but continue on the back side. In addition, the markings are not so much grooves and ridges but concentric terraces. My guess instead is some sort of abiotic sedimentary deformation.


James, J. F. 1885. Fucoids of the Cincinnati Group. Journal of the Cincinnati Museum of Natural History 7(4):151–166.

James, J. F. 1895–1896. Manual of the paleontology of the Cincinnati Group, Part VII. Journal of the Cincinnati Museum of Natural History 18(3–4):115–140.

Meyer, D. L., and R. A. Davis. 2009. A Sea Without Fish. Indiana University Press, Bloomington and Indianapolis.

Miller, S. A., and C. B. Dyer. 1878. Contributions to Paleontology 2.

Osgood, R. G., Jr. 1970. Trace fossils of the Cincinnati area. [regrettably, the plates are not included] Palaeontographica Americana 6(41):280–444.

Sunday, July 3, 2016

A locked dinosaur mystery

So, one of the things you're supposed to do if you have a blog is to talk about your research when a paper you authored comes out. Okay, give me a minute. I mentioned back in the gut contents post that I did my thesis on what was found in the inside of a brachylophosaur. The first part, on the gut contents themselves, was published back in 2008 (Tweet et al. 2008). Finally, after about a decade of gnawing on the manuscript, comes the other part (Tweet et al. 2016).

Sunday, June 19, 2016


After my years of puzzlement versus Leonardo, I have the greatest sympathy for the early generations of dinosaur paleontologists, being confronted with the often-scanty remains of beasts that had never been seen by anyone. We've already touched on Marsh dealing with Atlantosaurus and Cope dealing with Monoclonius recurvicornis. Ankylosaurians were no exception to the confusion. If a dinosaur skeleton is like a puzzle, a partial ankylosaur skeleton is like getting 300 pieces of a 2,000 piece puzzle, with the only guide being a hand-drawn copy of the box cover drawn by a right-handed person using their left hand, who is also in denial about the state of their vision. The puzzle, of course, is a stand of birch trees in a Great Lakes winter, in black and white. Small wonder that ankylosaurs spent most of the 20th century in the guise of magnified grouchy horned toads, covered in a pavement of armor laid out with enough regularity to satisfy the most tyrannical of 1950s suburb planners.

Monday, June 13, 2016

Cambrian island-hopping at Taylors Falls

Taylors Falls in the St. Croix Valley of eastern Minnesota presents an unusual geologic snapshot along a Cambrian coast. Within the south part of Interstate State Park, for an investment of a little more than a mile of walking round-trip, you can go from ancient basaltic islands, to the lithified rubble surrounding them, to the flanking sandy beach. Geologists love to try to paint verbal pictures of vanished settings, but rarely do the modern outcrops cooperate so nicely. Thank you to the park staff for suggesting an interpretative walk!

Sunday, June 5, 2016


Something I'd hoped to find at Chickasaw National Recreation Area was an example of Oklahomacystis. The Bromide Formation is one of the great rock units for echinoderm diversity, and Oklahomacystis is one of the classic forms. Unfortunately, we didn't end up getting into the Bromide in the recreation area, although it should be there, so it will have to wait for another time. I did see plenty of Oklahomacystis in the collections of the Sam Noble Museum, as well as one slab featuring a group of them at the Travertine Nature Center in the recreation area. Here are some photos of the slab:

Oklahomacystis tribrachiatus

Other photos of the same slab are on the Internet, but my photos may be the only ones without the glass, so they've got that going for them. The scale is important, because for some reason, when taken without it, the fossils look to be about the size of dates, when they are actually more like the size of the first joint of a finger. The fossils represent the body, or "theca".

Mysteriously larger

These are visually unusual fossils, looking something like a pine cone, or a pineapple, or a cluster of berries, or a grenade. A close look shows that their surfaces are covered by shared circular arrangements of six (usually) wedge shapes, kind of like Trivial Pursuit pies that share wedges with other pies. If you're familiar with the kinds of words that are frequently used in scientific names, you may have already guessed that we're dealing with an echinoderm. If you guessed "paracrinoid", congratulations, either you are really good with echinoderms or you already know something about Oklahoma's fossils.* A paracrinoid is one of the numerous varieties of stalked echinoderms that flourished for a relatively brief span of time during the Paleozoic and then went extinct. The name suggests affinities with crinoids, but it should be noted that sometimes they are classified more distantly, with relatives to blastoids ("sea buds") or as their own group distinct from either crinoids or blastoids. Like those two groups, a complete paracrinoid would have also featured a stalk attaching it to the seafloor. Presumably Oklahomacystis would have had a fairly simple feeding apparatus compared to crinoids, like the similar paracrinoids Amygdalocystites or Comarocystites (which looks quite a bit different because its thecal plates are strongly concave, giving it that "puckered hexagon" look that was such a craze in the Ordovician). Oklahomacystis had recumbent arms which are part of the thecal structure; as the species name "tribrachiatus" indicates, there are three of these (tri + brachi, meaning arm, which of course we know from Brachiosaurus, the "arm lizard". Snuck in a dinosaur!). Like the other two genera mentioned above, Oklahomacystis's filter feeding apparatus would have consisted of pinnules attached to the arms. If you'd like more technical information on paracrinoids, there's a monograph on the subject available here (no. 288; it just happens to name Oklahomacystis as well).

(*Oklahomacystis is sometimes identified as a cystoid echinoderm, as under the "Bromide Formation" page at Wikipedia. I hinted at this a little bit in a previous post, but in the past people have occasionally had recourse to shovel various enigmatic extinct echinoderms into the cystoids. I'd just stick with paracrinoids here.)

I'll be at an event for Interstate State Park next weekend, so expect some Cambrian in the next post. After that, I'll try to do something dinosaurian; otherwise they'll take away my card!

Friday, May 27, 2016

After-action from Chickasaw National Recreation Area

And so, "how did the PaleoBlitz go?", you ask. "Well", I would say. It's a work in progress, given that we'd never done one before, but I think the results were encouraging. As I mentioned, it isn't exactly the same as a BioBlitz, given that too much public exposure is often detrimental to fossils if you want to find them where you left them, but the parts about getting other organizations interested, and providing outreach to the public, those worked out just fine.

We had a core group of about ten people. Our park contact at Chickasaw National Recreation Area, who got things going on the ground for us, was Chief of Resources Noel Osborn. From the Washington office, in his capacity as the NPS paleontology program coordinator, was Vince Santucci. To better document Chickasaw NRA paleontology and to help with the event workload, we had two Geoscientist-In-the-Parks participants, Alysia Korn (recent graduate student at the South Dakota School of Mines) and Madison Armstrong (recent undergraduate at the University of Oklahoma). From the Sam Noble Museum/University of Oklahoma, we had the expert contributions of Roger Burkhalter (collections manager, invertebrate paleontology) and Steve Westrop (curator, invertebrate paleontology). In the field and at the public event, we also had the assistance of Clayton Edgar (Goddard Youth Camp), Steve Vanlandingham (Sam Noble Museum of Natural History), Don Weeks (NPS Natural Resources Division), and Dan Winings (Chickasaw NRA), as well as representatives from the Oklahoma Geological Survey at the public event. Finally, there was me, who was responsible for some of the background research, most of the photodocumentation (I got this position through the time-honored reason that I brought the camera), and a lingulid brachiopod that was not without merit.

Vince and I got into Oklahoma City on the 17th, and then traveled to Sulphur, Oklahoma the following day, spending the morning at the Sam Noble Museum on the University of Oklahoma campus in Norman, where we visited Roger and Steve, taped some brief interviews, and saw some of the collections. As part of the Centennial BioBlitz program, ours was one of the events tapped to provide a short video for the JumboTron on the Mall in DC; originally, we were told to have it in by the end of the day on Friday, but the deadline was pushed up to Wednesday, which in the end was probably a good thing because we all had to take a breather after Friday's fieldwork to prepare for Saturday's public event. You can see the original video here; the GIPs did practically all of the video editing, and I can't compliment them enough on how it turned out. On Thursday, we scouted several areas of interest for visiting on Friday.

Friday was our big field day. With a crew of Alysia, Dan, Madison, Roger, the two Steves, Vince, and myself, and some water transport courtesy of Clayton Edgar, we hunted for fossils in several areas, with primarily Ordovician rocks. Not to toot my own horn, but I found the second best piece, a large lingulid brachiopod at the first locality (the best piece for my money was a reworked crinoid calyx found by Steve Vanlandingham at a later site). Following an inviolate rule, I found it looking for a solid place to get a handhold; it wasn't solid, but things turned out all right. The weather was quite pleasant for Oklahoma in late May, with relatively cool temperatures, low humidity, and enough cloud cover to fool you into skipping sunscreen. I did lose a trilobite pygidium while engaged in a life-or-death struggle with the local plant life, so it wasn't a perfect day, but it was pretty good. The next day, Saturday, was the public event, which we held at the Goddard Youth Camp on the south side of the lake. Madison and Alysia have prepared a follow-up video, which can be seen here.

Finally, the stuff that people really want: photos!

The famous lingulid.

From left to right: Alysia (with brachiopod), Vince, Madison (foreground), and Steve Vanlandingham (background).

Another group shot in this picturesque area. L-R: Roger, me, Steve Westrop, Vince, Madison, and Alysia.

Steve Vanlandingham's crinoid calyx.

A reworked cobble of fossil hash.

Traveling on the Lake of the Arbuckles.

Dan Winings (left) and Steve Vanlandingham (right) traversing an outcrop featuring a carpet of wildflowers.

Echinoderm fragments.

A newly minted Junior Paleontologist.

Sunday, May 15, 2016

Out of the office...

I may not be able to write much for the next couple of weeks, because I'm going out of town for work. The back half of the trip mostly involves museum visits, but the first half is going to be a first-of-its-kind event for us, a PaleoBlitz at Chickasaw National Recreation Area in Oklahoma. What exactly is a PaleoBlitz? Well, it's something like a BioBlitz, only the subjects of interest are long past expired. How is it going to work? That, my friend, we're about to find out. It's Paleozoic marine invertebrates down there, though, and some of the rocks are about the same age as our own Platteville and Decorah, so at least there should be some familiar "faces". If you're going to be in south-central Oklahoma on Saturday the 21st, or are just interested in the concept, here's the public write-up and a more technical write-up about the festivities. See you later!

Saturday, May 7, 2016

Death Valley National Park geology, Part IV: Neogene and Quaternary

Very low-level photo across the salt flats of Badwater

...And finally we reach the top of the stratigraphic column at Death Valley National Park (DEVA). For convenience, here are the links to Parts I, II, and III. A lot of geologists just love the most recent 23 or so million years of Death Valley geology. For one thing, it gives people fantastic fodder for arguments about when various events happened, their extent, and even the basic mechanisms. DEVA features not only the pull-apart tectonics of the Basin and Range, but also lateral movements on strike-slip faults. As a result, there are depositional basins of a wide range of sizes. Terminology is a bit of a nightmare. The Wiki page on Death Valley geology isn't bad, but its strat column isn't a patch on the glorious Cenozoic complexity lurking in the park.

Thursday, April 28, 2016

Death Valley National Park geology, Part III: Mesozoic through Paleogene

We made it out of the Precambrian. We made it out of the Paleozoic. We aren't nearly out of Death Valley, though. There's still about 250 million years to go, during which the valley was converted from marine property to land, became gently toasted by massive subterranean plutons, and was eventually pulled apart into the modern topography over about 15-20 million years of nonstop faulting, with volcanic eruptions and inland lakes thrown in for variety.

Thursday, April 21, 2016

And the state fossil of Minnesota is...

...nothing. Despite the map on "List of U.S. state fossils," Minnesota does not have an official state fossil. There was a push to draft the giant beaver into this position, but the rodent fell short. The immediate political reason for its failure can be grasped from its scientific name: Castoroides ohioensis. Should the state fossil of Minnesota refer to another state? Certainly not!

Thursday, April 14, 2016

Death Valley National Park geology, Part II: Cambrian through Permian

When we left Death Valley National Park (DEVA) last week, we'd gotten partway through the Cambrian, into the early stages of a passive continental margin with shallow marine deposition. We return to find that predictable shallow marine deposition held sway until fairly late in the Paleozoic, when things got complicated in a hurry.

Thursday, April 7, 2016

Death Valley National Park geology, Part I: Proterozoic to Cambrian

As I mentioned a few months ago, one of the main components of my day job over the past few years has been preparing paleontological resource summaries for National Park Service Inventory and Monitoring networks. Between new and updated summaries, I've completed ten (Greater Yellowstone, Mediterranean Coast, Northern Colorado Plateau, Northern Great Plains, Northeast Coastal and Barrier, Northeast Temperate, Sonoran Desert, Southeast Coast, Southern Colorado Plateau, and Southern Plains). Each network has its own foibles and presents different challenges. Some are much more easily tackled than others; smaller parks generally have less to worry about than larger parks, with small urban cultural or historical units usually being the simplest. After finishing the Southern Plains Network last spring, I knew that the Mojave Desert Network (MOJN) would be one of the obvious candidates for the next project. It was completed under a superseded format, so it was already in the hopper, and we were already working with Death Valley National Park and Lake Mead National Recreation Area, so the iron was hot. The attraction for me was the challenge. The MOJN parks have superb geological records exposed by the combination of Basin and Range faulting and restricted plant cover, and they cover vast areas.