It’s been a wild month. I’m writing from a fjord in southern Norway, where I’m (finally) on vacation after teaching a four-week field mapping course around the Tetons in Wyoming. This was my first teaching experience, and I was pretty nervous going into it. As a geochemist, structural mapping isn’t exactly my tofu and potatoes, but having been out to the field sites before gave me an edge of confidence I certainly wouldn’t have had otherwise. And, as it turns out, teaching mapping in the foothills of the Tetons is pretty incredible. Exhausting, but incredible. (Here’s what I learned!)
We began the trip with a two-day caravan heading out to Colorado, where we would start our first regional field trip. Camping in Nebraska in the middle of July is unspeakably humid, and I’ll just leave it at that. Once we arrived in Colorado Springs, we loaded up on groceries and headed off into the mountains, into a decently torrential storm. Our camp was cold, wet, and (as far as some of the students were concerned) filled with bears. The next morning, though, we packed up and drove into the mountains for our first day of geology. In five days, we covered pretty much all of southwestern Colorado and northeastern Utah. The students learned how to recognize normal fault systems, paleosol floodplain sequences (thanks to me pointing out every one that we drove by), high-angle reverse faults, and so much more. We visited the Black Canyon and its stunning exposures of Precambrian basement. We listened to bizarre public radio in rural Utah. We visited Dinosaur National Monument and camped under the stars at Sheep Creek in Utah’s Flaming Gorge Recreation Area (fanning the flames of my ongoing love affair with Utah geology). It was an excellent way to kick-start field camp.
U. Michigan / UT legend John Geissman teaching the students about the
The Black Canyon. Probably the most impressive canyon I’ve seen. It’s SO OLD.
The view from a Sheep Creek overlook on the geologic route.
Speed-sampling Chinle Fm. paleosols for my terrestrial iron timeline.
Once in Wyoming, we wasted no time! On our first day, we were lucky enough to be able to see a paleoseismic trench that was being opened in the Teton national park for a USGS study on the Teton fault, which is still active. The trench would only be open for five days, and the USGS folks were nice enough to take an hour or two and show us what they were working on.
After that, we jumped right into our first mapping project, which was meant to introduce students to measuring stratigraphic sections and get students’ rock ID skills warmed up. The rocks were all sed rocks representing transgressions and regressions, which – to some of the students’ dismay – meant rather a lot of jaking up shaley slopes. This was done near Slide Lake, which was the site of a catastrophic landslide that dammed the river, which later burst and flooded the town downstream. The hillslopes still bear evidence of this event, and looking around the valley, it was easy to pick out marks of other, smaller slides.
Once the students had their intro to stratigraphy, we moved onto a Michigan classic: the Jurassic Red Hills in the Gros Ventre region in front of the Tetons. Here, we were mapping some basic structures (faulted anticlines!). People were a little winded – first day hiking at elevation – but the views of the distant Tetons at lunchtime made the effort worth it.
The projects got a little longer after those two introductory sites. Mapping the slopes above a segment of the Snake River was the students’ first chance to really put together what’d they’d learned and apply new skills to a more comprehensive mapping project: identifying rock units, describing lithology, identifying structures, and not getting eaten by bears or attacked by moose. (All important skills.) We lucked out and got great weather for our Wyoming work… until the end of day three. After leaving a rather exposed hillslope prematurely due to the development of some threatening clouds, we were looking at roadcuts (some of which contained huge nodules, more on that later) to round out our stratigraphy when the sky began to darken. When the first drizzles began, no one took much notice. Pretty quickly, though, the drops got bigger and hit harder. Just as we were beginning to think that we should head back soon, a car whizzed by but took the time to roll down a window and shout, “There’s crazy hail coming! You’d better get inside!” No sooner did they peel around the curve then we saw a thick grey wall hightailing down the road, straight at us. Cue everyone sprinting back to the vans, still carrying what cool rocks they could. The hail hit just as the last van door slammed shut, and we hunkered down in the parking lot for five minutes or so while we waited out the worst of it. All I could think was that I was glad I trusted my gut on the mountain and voted to head down. (I’ve been caught in a mountain storm once too much for comfort.
N = 2.) A fine way to end a project.
After that project, the students had a free day, which meant they went hiking and swimming and we (grad students) did some sampling. I drove back to the Snake River outcrops to investigate those huge nodules I’d noticed. I had actually seen them before, when I was out here for my own field camp, but I hadn’t been able to find any in place. This year, however, I located a bunch in place, situated in purple-red claystones with slickensides which I suspected of being paleosols. My first thought was that these were huge iron-rich carbonate nodules (siderite), forming in floodplains, but there was no reaction with acid. Their structure is pretty neat: not one smooth concretion, but a bunch of blebs packed together, each with its own radial internal crystal growth. I want to do XRD or something to see what it is… a future project.
The suspected paleosol, which I sampled for Fe analysis.
Anyway. Our next endeavor was the students’ choice, actually: either they could go camping at the tip of the Wind River range and map metamorphic rocks and banded iron formations with all-things-magnetic-legend John Geissman, or they could do a LiDAR project of a truly huge landslide with tectonics professors Marin Clark and Nathan Niemi. While LiDAR proved to be the more popular option (I guess people were sick of camping and mapping rocks), we had a great little group that headed out to the middle of Wyoming and set up camp at an idyllic site, complete with babbling brook and far away from bears. Prior to this, I had absolutely zero experience mapping metamorphic rocks, so this particular venture was as much a learning experience for me as it was for the students. It was such a fantastic trip, and I carried back literally about a hundred pounds of rocks. (My friends called it “an irresponsible amount of rocks.”) I was able to have some great conversations with John about rock magnetism and the issues with using paleosol magnetic signals and minerals, and I really enjoyed learning along with the students.
Once we parted ways with the BIF, the class left pretty immediately for a short trip through Yellowstone and the surrounding region. On this trip, we covered the history of the mantle plume and the line of Yellowstone eruptions, as well as the petrology of different basalts we came across. All in all, it was a gentle end for field camp before the long, long drive back to Michigan.
After two crazy days of driving, we reached our final campsite: Indiana Dunes State Park. Even though I’ve lived in Michigan for essentially my whole life, I’d never been out there. We were treated to a gorgeous sunset over Lake Michigan, with the lights of Chicago visible across the water. It was good to be back home after four weeks of constant work.
Clouds ringing the Tetons, above Teton Lake.