Postdoc Spotlight: Geochemist Jesse Reimink

Jesse Reimink
Friday, February 17, 2017 

Jesse Reimink has been around science and the outdoors his entire life. His father, a high school biology teacher, would keep him and his sister busy searching for rocks and insects outside for their collections. He and his friends would go on camping trips every summer where they collected rocks while braving rattlesnakes, snow, and local ranchers. After his high school teacher energized him toward the field of geology, Reimink knew he wanted to study the Earth and the rocks that formed it when he started his undergrad. Today, as a postdoctoral associate at DTM, his rock collection has grown exponentially. This summer, he collected over 1200-pounds worth of samples from the Slave craton, a block of rocks in north-western Canada that has preserved a lot of old rocks ranging in age from 4 billion to 2.5 billion years old.

We spoke to Reimink about what he likes most about his field of research, and where he sees his career in the future following his postdoc at DTM.

Taking a break on the outcrop. On DTM Postdoctoral fellow Jesse Reimink's right side (beneath the green pack) is a small, rare, valuable window where there is no lichen covering the rocks and we can actually see clearly what types of rocks are underneath.  These little windows are commonly called "caribou piss spots" with the idea that caribou urine kills the lichen in small areas.  Reimink was totally unconvinced that this was true until this past summer when he saw fairly convincing evidence that this was actually what was going on in our first campsite near a major caribou migration route. Photo courtesy of Jesse Reimink, DTM. 

DTM: When did you first become interested in your field of research? Why? 

Jesse Reimink: Growing up, my dad was a high school biology teacher, so I was always around science and the outdoors. However, it was not until 9th grade that I was first introduced to Earth science and geology.  My high school teacher, Chris Bolhuis, is a superb teacher and motivator (he won the National Earth Science teacher of the year award from the American Association of Petroleum Geologists a few years back) and really energized me toward the field of geology.  From then on I knew that I wanted to major in geology when I started my undergrad. 

DTM: How did you first hear about DTM? What brought you here?

Reimink: I heard about DTM midway through graduate school at the University of Alberta.  One of my advisors, Graham Pearson, is an alumnus of DTM. He and my supervisor, Tom Chacko, strongly suggested it to me as a place to go for a postdoc.  I also met Steve Shirey on a field trip through the famous Franciscan complex rocks in 2013.  The rocks in this area are classic examples of what happens to the oceanic crust as it is subjected to intense pressure during subduction.  Now these rocks, formerly part of the ocean floor, have been metamorphosed and exposed to the surface in the areas around San Francisco.  This field trip was guided by a local expert and associated with the Goldschmidt conference.  Steve, my supervisor Tom, and I went for a beer after looking at these great rocks all day, and we talked about the fascinating science going on at DTM and the excellent lab facilities available here.  This conversation really cemented my desire to come to DTM.  

Supervising as Graham Pearson (former DTM postdoc) takes a sample during Summer 2016 fieldwork in the NWT of Canada.  Photo by Steve Shirey, DTM.

DTM: What excites you about your work? 

Reimink: The thing that really excites me about my work is answering basic questions about how the Earth operated in the past.  We have a (somewhat) decent working model for how rocks form on the modern planet, but we really do not know if the processes we see happening on Earth today were the same in the past or not.  It is extremely difficult to answer these questions because there are so few samples preserved from early in Earth's history. For all we know, it could have worked in a manner we have not even considered yet. 

Another aspect of my work that really excites me is the combination of fieldwork, lab work, and analysis, it entails.  In our work we do almost everything in this workflow, starting in the field where we collect rocks in secluded places like Canada’s remote Northwest Territories (I walked across some of the oldest known rocks on Earth this past summer!), followed by rock crushing and mineral separation in the lab, ending with valuable analyses to determine the varying ages and chemical compositions of these samples.  To me, control and a fundamental understanding of the complete process allow for better interpretation of much of the very complicated data we collect as geochemists. I like to be involved as much as possible at every stage (maybe I’m a bit of a control freak…).  I also love doing fieldwork and spending time in remote places where very few people have ever walked before!  

Excellent exposure of very old metamorphic rocks in the Acasta Gneiss Complex, NWT, Canada. Parts of this outcrop contain the oldest bits of continental crust that we have so far discovered on Earth. The background is typical of the Canadian tundra, with very few trees, lots and lots of water, and short, rolling hills. Photo by Jesse Reimink, DTM.

DTM: What research projects are you working on now at DTM?

Reimink:  Right now, I am working mainly on a project funded by a National Science Foundation grant awarded to Steve Shirey and Rick Carlson.  For this project, we traveled to the Slave craton, a block of rocks in north-western Canada that has preserved a lot of old rocks ranging in age from 4 billion to 2.5 billion years old.  Using the samples we collected during our fieldwork in the summer of 2016 (for parts of this fieldwork we were accompanied by Carnegie President Matt Scott, Carnegie Trustee Member Mike Long, and former DTM postdoc Graham Pearson), we are investigating how continental crust formed over 1.5 billion years of Earth’s history in one location, which is a unique opportunity.  The Slave craton provides a unique location to study these processes because it preserves rocks with such a large range of ages.  Additionally, the mantle beneath the Slave craton is relatively well studied, as there are major diamond mines in that part of Canada (many of which Steve and Graham have worked on previously), and the ability to link the evolution of ancient crust with the chemical evolution of the mantle beneath it provides a unique setting for investigating how the Earth operated during this time. 

I am also working on a few other projects that are focused on data reduction methods and finding new ways to evaluate complicated datasets.  This is a line of research that is pretty fascinating to me and is providing some interesting results.  Colleagues and I have published one particular method that aids in the interpretation of complex U-Pb ages from zircon grains (a very robust mineral used for geochronology) in a statistically meaningful way.  Using this method, we are investigating how certain types of granite rocks are formed, and we think we can actually pinpoint the specific sedimentary rock units that are being melted to form these granites.  We are also looking into ways to model other complicated datasets, like oil and shale Re-Os isotope data, and are seeing some interesting results coming out of that type of data analysis.  The geochemistry community is continuing to measure more samples more rapidly, so datasets are becoming larger and more complex, necessitating new methods to interpret them.  I think this is a very interesting field that will hopefully come up with some new results and highlight interpretations that were previously inaccessible to geochemists.  

I’m also involved in working on a few crazier ideas with colleagues.  One in particular that I’m pretty interested in involves using glacial sediments to trace the compositions and ages of rocks exposed at the surface.  Much of northern Canada is relatively low-lying, very remote, expensive to get to, and difficult to map with traditional geologic methods.  These areas were also fully covered by ice (the Laurentide Ice Sheet) during the last major glaciation event, and as the ice sheet melted, sediments were deposited on top of the rocks.  With Alberto Reyes, a professor at the University of Alberta who is an expert in glacial sediments and northern fieldwork, we are looking to see if the deposits left by these glaciers can be used to trace the ages and compositions of rocks that were “upstream” of the glaciers, and use it to “map”, in a non-traditional sense, large areas of the Canadian Shield that are either inaccessible, very expensive to get to, or would take an extremely long time to map traditionally.  This project probably has little chance of success, but it is a cool idea that, if successful, would really give geologists new tools to understand the geology of remote northern lands. 

Studying a geological map, and trying to decide where to go next (or maybe where to eat lunch), during Summer 2016 Fieldwork in the NWT, Canada.  Rick Carlson (left), Steve Shirey (bending down in the back), and Mike Long (Carnegie Board Member; kneeling in the blue shirt) supervise the very important decision.  Photo by Matt Scott, Carnegie Science.

DTM: What research do you hope to do in the future?

Reimink: I don’t typically think all that far ahead regarding research direction, instead I just pursue what seems to be the most interesting thing at the moment.  Broadly, however, I would hope to continue in similar research themes as I am working on now, as well as open up new lines of collaboration with other people from different fields.  The sample set we took back with us from the Slave craton this summer contained roughly 200 samples and weighed over 1200-pounds, so there are plenty of very exciting projects to develop with these rocks!  I will probably continue to work on various samples from this fieldwork on and off for many years to come.  There are constantly new analytical techniques being developed for studying rocks and minerals, and I hope to apply some of these new, cutting-edge techniques to the sample suite we have collected, and answer some fundamental questions about how the Earth operated ~3 billion years ago!

I am also interested in getting involved in studying more modern rocks and the processes that lead to their formation.  I said earlier that the community has a decent working model for how modern rocks are formed, but that is only in the most basic sense.  There are all sorts of fundamental details that are currently being studied (many of them at DTM and the Geophysical Laboratory), and I think the field of modern igneous petrology is really an exciting place to be right now.   

DTM: What do you hope to be doing at your next job? 

Reimink: Ahh, the classic question for postdocs.  The short answer is that I have no idea.  I really love being at DTM and will try my hardest to hang around as long as possible!  I have been applying to assistant professor positions and would like to stay in academic research in some capacity, but it is not clear what that looks like at the moment.  I do like teaching quite a bit and could see myself in a smaller college setting, or continuing to work in a research-heavy place similar to DTM.  We will see what happens.

Unsuccessful fishing attempt (it wasn't Reimink's fault, there were basically no fish in the whole lake) during a lull in the fieldwork action at Brown Lake, NWT, Canada.  Summer 2016.  Photo by Steve Shirey, DTM.

DTM: Where do you see yourself in 10 years? 20?

Reimink: I am honestly not sure.  So far, I like what I am doing and the research I am working on is pretty interesting.  I have never really planned that far out because these academic jobs are so unpredictable.  I guess a lot depends on what happens the first few years when I leave Carnegie.  Ultimately, I would like to be in a place where I can do the most interesting research and live in a cool area.  Where that is, I am not sure yet!  I must say, staff members at DTM seem to have a pretty nice setup and I wouldn’t be surprised if most postdocs that came through here would love to come back as staff. 

DTM: Any other interesting anecdotes about your life you want to share? 

Reimink: I had a really awesome rock collection as a kid, or at least I thought it was awesome but it was probably like any other kid’s somewhat lame rock collection.  My collection is much, much better now; a few friends and I would go on camping trips every summer where we collected rocks while braving rattlesnakes, snow, and local ranchers.  Despite some claims, all of the rocks in my collection were sampled legally, more or less. 

I also had a pretty sweet butterfly and moth collection as a kid.  Surprisingly, my sister and I both survived our insect collecting trips because of our father, the biologist, gave us both jars with potassium cyanide in them to kill the insects.  He just told us to “not breath in when the jars are open.”  In unrelated events, I got the unfair reputation for breaking lab equipment while at the University of Alberta.  Machines would mysteriously stop working when I wanted to process samples, and certain people chose to blame me.  In my opinion, what was happening was that everyone wanted to start fiddling with routines just when I started working on them, and I think the fact that I have not caused too much damage here at DTM (knock on proverbial wood) validates my opinion. 

Jesse Reimink
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Interview by Robin Dienel, February 21, 2017

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