Where to see metro geology, part 1: Lock and Dam No. 1

As the snow and ice begin to melt away and the temperature rises above freezing, it once more becomes possible to see the geology of the metro without outfitting a polar expedition. While there's something to be said for iced-over waterfalls and the peace and stillness of a fresh winterscape, it's darned hard to take field notes with choppers on or fogged-up glasses, and frankly if you're doing it to impress people, it won't work. Spring is not a bad time to do some exploring; you don't have to contend with the bugs, the generous Minnesota humidity isn't in full swing yet, and the ground vegetation hasn't obscured many areas (and given ticks places to loiter). The most obvious drawback to springtime geology is the saturation of the ground, particularly in places where the Decorah Shale is at or near the surface. The Decorah likes to form a thick gray-green mud that both cakes footwear and makes the ground admirably slippery, particularly on slopes where you'd just as soon prefer that it wasn't slippery. Throw in the leaf litter from the previous fall, and your April hike can get a lot more interesting. A less-obvious hazard is the insidious action of freeze and thaw cycles. In short, rocks that weren't fractured and liable to fall or slide in the autumn can get that way by the spring.

Dinosaurs in limbo

Following paleontology can be a bit like getting presents on birthdays or Christmas or what-have-you. Sometimes you get completely knocked out by something, having had no idea it was on the way. Sometimes you know what's coming, and it's just a matter of waiting for the big day. Sometimes it gets held up in the mail, or the store's out and it's on back order, so you still know it's coming, but you don't know when. Finally, in a few cases it seems like the darn thing got lost somewhere. As of the time I am writing, March 22/23, the latest greatest dinosaur discovery in the news is the "chicken from hell", Anzu wyliei, a 3-m long distant relative of Oviraptor from, fittingly, the Hell Creek Formation of Montana ("Anzu" being a reference to a Sumerian demon). My first reaction was "Finally!" You see, Anzu had been floating around for years under various nicknames like the "Hell Creek Chirostenotes" or "Chirostenotes sp.". It was quite familiar to the dinosaur paleontology community; it was just a question of when it would be described.

On the Arctic Cretaceous

By now, those of you who follow paleontology news have probably heard of Nanuqsaurus hoglundi, the newly described genus and species of small Arctic tyrannosaur. The obligatory and nearly instantaneously produced Wikipedia article can be found here, and the scientific description can be found here. Nanuqsaurus comes from rocks of the North Slope of Alaska, and lived about 70 million years ago. It's just the "tip of the iceberg", so to speak, of the North Slope dinosaurs, which also include the hornless horned dinosaur Pachyrhinosaurus perotorum, a bonehead named Alaskacephale, the ubiquitous duckbill Edmontosaurus, and various small theropods. This is pretty typical for the latest Cretaceous of North America, give or take an armored dinosaur.

Fossils in the St. Peter Sandstone

The St. Peter Sandstone, a Middle–Late Ordovician unit that deserves the appellation "sandstone" like few other formations, has proven itself a very useful formation. Its extremely pure quartz sand is prized for various industrial applications, like glassmaking. It is readily excavated, so digging sewers and burying utilities is simplified. It has a tendency to form caves, which coupled with the ease of excavating makes it an ideal substrate for underground storage, cheese aging, mushroom growing, some types of brewing, and so on. More frivolously, it has provided a vast natural canvas for people who like to carve their names in things, and it has rewarded generations of graduate students looking for thesis and dissertation topics. At 100+ feet (30 m+) of uniform sand with few apparent bedding structures, and an off-white color that weathers to a kind of sickly gray, it is also an excellent natural soporific if you are not interested in any of these things. This most useful of formations is very much a bust paleontologically, which seems like some kind of a metaphor, but I'm not going to push things.

Ordovician microbial mats, featuring the Gopher Ordnance Works

Here's a little curiosity, bringing together a short-lived ordnance plant, Early Ordovician sea scum, and Clinton R. Stauffer, who seems to have become a patron saint of this blog through the first couple of months. Let's deal with the ordnance plant first.