Structural Geology & Tectonics @ ETHZ

Authored by Lonnie Hufford.

This post is about my second field season in Alaska. You can read about my first field season here: https://structuretectonics.org/2019/08/22/fire-and-seagulls-a-game-of-rocks/

Prof. Whitney Behr, Dr. Mark Helper, Dr. Zoe Braden, and I completed another field season this past summer in southern Alaska. Over the course of a month, we traveled the Kenai Peninsula using boats, planes, and cars to conduct our research, work and camp with some great people, and see many animals (some closer than we wanted to).

Our next album is dropping soon. Seldovia, Alaska.

The face you make when you encounter a bear on the trail. Behind us is Halibut Cove, Alaska.

Seldovia, Grewingk Glacier, the Soldotna region, and Turnagain Arm were our featured field areas this season. At these locations we collected samples, structural measurements, made notes, and mapped with drones and Ipads. For our projects here we are studying several units located in an exhumed accretionary wedge: the Seldovia schists, The McHugh Complex, and the Valdez Flysch (from oldest to youngest). We are interested in the rheology at the shallow subduction interface and the exhumation of subduction interface rocks. The mélange shear zones, multiple generations of brittle faults, and, in the Seldovia region, juxtaposition of high pressure-low temperature to low-grade metamorphic rocks lend themselves to many different questions such as how strain is localized along strike among mélange shear zones with different matrix material, what is the effect of fluid on these mélange shear zones, and what is the overall structural history of these units?

Whitney and Mark in the distance on one of the beautiful Seldovia beaches. If you keep an eye out and listen, you may just find a bald eagle along the beach when doing field work.

The view of Grewingk Glacier from my packraft.

In Seldovia, my field area, I am interested in the Seldovia schists,  their deformation and exhumation history, and how they are juxtaposed against the McHugh Complex, a younger unit of lower metamorphic grade. Something new we did this season was create 3D maps of many of the outcrops in Seldovia. This technique allows us to better map, take notes, and just revisit the outcrop even though it’s across the world. This new frontier of field geology will be an effective way of bringing the reader to the outcrop so they can see and interact with the rocks. If you are interested in viewing some of the early stage drone maps please visit Whitney’s sketchfab account: https://sketchfab.com/whitney.behr/models

A 3D model from Seldovia made with drone imagery. We used a Mavic 2 drone with Agisoft MetaShape Pro software to create these models.

You don’t always need bright, sunny days to do field work. When the tide is low, you gotta go! Seldovia, Alaska. *This beautifully folded McHugh outcrop is inaccessible at high tides.

The data from my first field season has been quite interesting with titanite geochronologic, raman thermometry, and quartz- and apatite-in-garnet barometry data which were presented in a digital poster format at the (online) GSA 2020 conference. The data we will add from our most recent field season will allow us to explore the structural and tectonic history of Seldovia and southern Alaska even more!

Being able to visit the field during such hectic times was logistically challenging, but we were rewarded with a fantastic field season. As we visited new locations and saw more outcrops (such as the beautiful intercalated blueschist and greenschist in the photo), while revisiting “old outcrops” with fresh eyes, I simultaneously gained a deeper understanding of the rocks here while developing more questions. I believe that’s how a field season should go. 

Intercalated blueschist and greenschist in Seldovia. 

Now I am in the process of hunting for zircons so we can gain a bit more insight on the rocks in Seldovia. See you next field season Alaska!

Animal (path) Crossing

We crossed paths with two moose, a bear, and otters on this trip (in order from most terrifying to most eligible household pet). The bear decided to bumble across our path in the morning without caring too much about our presence. The two moose, however, decided the trail would be a perfect spot to chill. They presented us an opportunity to forge our way through the forest for an added sense of adventure.

This super moose never misses a day at the gym. We took care not to get close to him.