Compact Thescelosaurus Year Eight

It's that time again, for National Fossil Day (October 11 this year), a new sheet for The Compact Thescelosaurus, and the annual summary of what was added to the spreadsheet in the past 12 months. In addition to National Fossil Day events this month, the latest issue of Park Paleontology News is up for viewing. Also in breaking NPS paleontology news: additional dating of the fossil human tracks at White Sands National Park, and a previously overlooked record of a tyrannosaur tooth at Yellowstone National Park. [Update, 2023/10/10: And a tritylodont bonebed at Glen Canyon National Recreation Area was just announced; goes well with this new paper on a massive track block from the recreation area, too.]

Here at Equatorial Minnesota, we've passed 400 entries this year. Later this year, December 15 will mark 10 years of posting. (Also, anyone know why this nautiloid post would have spiked in interest?) The Compact Thescelosaurus has been around for 8 of those years, and it's traditional to add a new sheet. For this year, first I considered all of Pseudosuchia (except for the aetosaurs, covered already), but decided against it due to the number of species. I then looked at doing just Mesozoic pseudosuchians before being discouraged by whatever it is Thalattosuchia has been doing over the past 200 years. So, for now it's just Triassic forms, with the intent to expand over time.

Prestosuchus threatening an Eoraptor in the "Ultimate Dinosaurs" exhibition at the Science Museum of Minnesota, May 2014.

Compact Thescelosaurus Year Seven

Here we are at the second weekend of October, which means it's time for three things: National Fossil Day; a new sheet for The Compact Thescelosaurus; and our annual roundup of what's been added to the spreadsheet. National Fossil Day falls on Wednesday, October 12 this year, although events occur throughout the month (especially the weekends before and after), so check your nearest museum or National Park System unit for events! Our fall Park Paleontology newsletter is also up for viewing (including more fun with packrats).

Compact Thescelosaurus Year Six

The time has come again for the annual review of The Compact Thescelosaurus. This year's new page is on aetosaurs and their close relatives, with the classification diagram page updated. (Don't forget, Wednesday the 13th is also National Fossil Day!)

Aetosaur Desmatosuchus spurensis is one of the subjects of the NPS Prehistoric Life Coloring Book. Coincidentally, an aetosaur also featured in the 2014 National Fossil Day artwork.

At the Grand Canyon

When I left off back in October, we'd just left Flagstaff for Grand Canyon National Park. The object of my visit was to support a paleontology project at Grand Canyon National Park, including our big National Fossil Day event.

The event is over now, but you can still see things like this display put together by GIPs Diana and Klara with park staff. As usual, I was too caught up in working the event to take a lot of pictures.

Of course, people who are interested in geology hardly need to be told to go to the Grand Canyon.

Pictured: geology, as far as the eye can see.

With billions of years of geological history on display, showing evidence of everything from high-grade metamorphism, to volcanic eruptions, to sea level changes, to eolian processes, to cave formation, there's something there for just about every area of geological study. Granted, a lot of things aren't immediately accessible due to the whole "enormous canyon" factor, but even if you've only got a few hours you can visit the historic Yavapai Geology Museum and take a quick tour of the park's geological formations on the Trail of Time.

Left: entering the trail. Right: a time marker, from near the "present" end of the trail, where time is less compressed.

The Trail of Time uses a series of time markers spaced evenly along the trail, with a couple of shifts in the order of magnitude. For example, starting from the Yavapai Geology Museum, the first markers are yearly. Pretty soon, though, the markers are for every million years. As you go along, stones from the various formations are placed according to their ages.

A couple of examples. Left: a close view of the stromatolitic rock chosen to represent the Awatubi Member of the Kwagunt Formation. Right: the Sixtymile Formation is one of the most obscure units of the Grand Canyon, and actually has had its age revised significantly since the Trail opened in 2010; it's now known to be early Cambrian in age (Karlstrom et al. 2018). This particular sample bears a striking resemblance to a Nut Goodie bar.

Once you get used to the rocks, you'll become able to pick out the different formations at long distances.

As the display shows, the top four formations of the Canyon can be readily picked out. Below the Hermit Formation is the Supai Group, which is responsible for giving the underlying steep cliffs of the Redwall Limestone its red walls (it's naturally gray).

There are also many trails which offer glorious views and the opportunity to commune closely with the rocks. (Don't plan on hiking to the bottom and back up in one day, though!) I went down part of the Grandview Trail as part of a day survey.

And it certainly lives up to its name! Try identifying the upper formations using the previous image.

There's also some human geological history of the Canyon at the Grand Canyon Pioneer Cemetery, where several notable geologists and paleontologists have been laid to rest. Edwin "Eddie" McKee is the person most indelibly associated with the Canyon, having quite literally written the book on most of the sedimentary formations of the park, but there are also: Bill Breed of the Museum of Northern Arizona; John Maxson of the California Institute of Technology; Glen Sturdevant, the park's first naturalist; and David White, who described the park's plant fossils in the 1920s. Some of the species described by White are depicted on his monument.

It's a little difficult to make out the plants, but they are present in three of the four corners of White's plaque.

Just keep an eye open for wildlife...

Foggy mornings are a lot less frequent than elk.

Aphonopelma marxi (a.k.a. A. behlei) enjoying a walk on the Trail of Time.

References

Karlstrom, K., J. Hagadorn, G. Gehrels, W. Matthews, M. Schmitz, L. Madronich, J. Mulder, M. Pecha, D. Giesler, and L. Crossey. 2018. Cambrian Sauk transgression in the Grand Canyon region redefined by detrital zircons. Nature Geoscience 11:438–443. doi:10.1038/s41561-018-0131-7.

What I Did While I Was Out: On the Way to the Grand Canyon

As I mentioned a few months ago, I've been spending a lot of time on the fossils and rocks of Grand Canyon National Park this year. Part of why I've been doing this culminated on Saturday, September 28: our special National Fossil Day event, held at the park as part of their centennial festivities. (You can see the whole group that worked the event here.) We've been working for months on a Grand Canyon NP paleontological inventory, and to further that work as well as help at the public event, I spent the end of September in Arizona, visiting various places.

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!

Port Kennedy Bone Cave supplement

The National Fossil Day monthly feature for September is Port Kennedy Bone Cave (archival link here; added 2018-03-14), 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.

National Fossil Day 2014

Here in the States, the leaves are turning color, the GSA/SVP conference season is at the doorstep, and National Fossil Day is upon us. This event occurs on the Wednesday of Earth Science Week, fittingly enough, which this year is the 15th. National Fossil Day includes a number of local events across the country, although not all of them are on Wednesday; for example, in the Twin Cities, early readers might be able to catch a fossil and geology event at Coldwater Spring from 9 to noon on Saturday the 11th (and the weather's looking good, too, which is a bonus for mid-October in Minnesota; last year we held a fossil and geology walk the Saturday after National Fossil Day, and just after we finished we had a downpour of ice pellets). If you're unable to get to Coldwater Spring, are busy that day, or would prefer an indoor event, the Science Museum of Minnesota is holding Fossil Day on Saturday the 18th. Of course, there are also plenty of places along the bluffs if you'd just like to spend some time among the fossils in their natural setting before it gets too cold. The flagship events are held in Washington, D.C. In previous years events were held on the National Mall, but because of construction they have been shifted to the National Museum of Natural History. If you're in D.C., I also recommend checking out the building stone as you're walking around; the city has an excellent fossil record on display.

You might think this is an armored dinosaur, but it's actually an aetosaur, a Triassic offshoot of the group that includes crocodilians. The story behind the logo can be found here.