When Georneys announced that June’s Accretionary Wedge Global Carnival was “What’s your favorite geology word?” I knew that this would be the perfect launching post for this blog. As a physical geographer, an ice-age ecologist, and a frustrated English major, I have a lot of favorite geoscience words (where else do you get to say words like “drumlin,” “foraminifera,” and “roche moutonnée”?). If I had to pick just one, however, I’d have to go with gyttja, the fine-grained, nutrient-rich organic mud that accumulates at the bottom of lakes and bogs.
“Gyttja,” pronounced “yit-chah,” is a Swedish word; some of the pioneers in Quaternary studies have come from Sweden, but I’m guessing the real reason the word stuck with English-speakers is because it, like “loess,” is so fun to say. I’m sure some would argue that it’s not a proper geology word — I’ve heard more than one hard-rock geologist refer to my research material as the “late-Cenozoic overburden.” Some Quaternary scientists dismiss the term as not terribly informative (these are often the type that painstakingly match mud colors to a Munsell chart; to each their own).
But I love gyttja– I love spending long summer days on a floating platform the size of a picnic table, bringing up meter after meter of sediment core from the bottoms of the small kettle lakes that are my field sites. I love watching the sediment transition from dark, organic-rich mud to the lighter silts and dense grey clays as the core segments get deeper– essentially time traveling via mud, as roughly a thousand years of time are captured in each meter. I’ve even eaten gyttja (a rough field test for the presence silt is to put a bit on the tip of your tongue and feel for grit against your teeth).
Most of all, I love bringing gyttja back to the lab to reveal the microscopic material preserved within, dissolving and sieving away the silts, clays, and organic material to find the pollen, charcoal, and other paleoenvironmental proxies my lab uses to reconstruct the environments of the past. My parents and friends don’t always understand what I do as a grad student, but they’re not terribly surprised that I still play in the mud.
What are you using as a core liner? I’m still trying to find a decent (read: cheap) source.
When you say “core liner,” I’m not sure exactly what you mean (i.e., the polycarb or pvc mentioned below?), so I’ll describe our entire system if that’s helpful. We start with a Bolivian adapter to our Livingstone corer to capture the first meter or two of really flocculant sediment– the Bolivian allows us to core with a polycarbonate tube as the core barrel instead of the Livingstone’s steel barrel. We add a little Zorbitrol to the top of the first drive, which turns the water into gel and stabilizes the core top, and then tubes get capped on both ends and taped.
Then, we shift to a 4″, 3″, and/or 2″ Livingstone piston corer (we start with the biggest and move downward as sediment gets stiffer), and we extrude our cores right on the deck of the platform. The photo in the post above is of an extruded core. We extrude directly into a piece of split pvc, and then wrap with plastic wrap and aluminum foil (we put a layer of plastic wrap over the extruded core, place the other pvc half on top, flip it over, take the first pvc off, finish wrapping the plastic, then repeat for aluminum foil). The two pvc halves then get duct taped together (with the ends capped with duct tape!).
We take the cores to the Limnological Research Center’s core facility at UMN where they get split longitudinally (they have a nice saw to split the polycarb tubes). Sadly, the polycarb tubes are single-use, but we reuse our pvc (we have 4″, 3″, and 2″ sets).
I hope that helps!
That does help. I’m using some of the AMS soil coring tools – a 12″ split core sampler and a 4″ steel tube sampler (similar to livingstone, it just uses a slide hammer to drive the corer into the soil). The 2″ clear polycarbonate liners that would go inside are ridiculously expensive per foot (and would be a one-time use item). I like the idea of pre-split PVC. I’ll have to try that method. One of my biggest problems is that I’m tying to extract terrestrial soil cores – lake muck would be much easier on the setup. But a split PVC liner might allow me to extract the core itself w/o too much trouble.
Do you have much trouble extruding the collected cores?
Ah, that makes sense. That does sound much tougher than what we have to deal with. We generally don’t have trouble for the more organic sediments, but stiff clays and sand layers can be difficult to extrude by hand – we’ve used a come-along winch in the field for pesky stiff cores. Only once, in really carbonate-rich mud with lots of marl and sand layers, have I had to scrap a drive. We had to shoot water up the barrel with a super soaker to get it out!
Welcome to the geoblogosphere! In fairness to Quaternary geologists, I have heard the term “Pre-Quaternary underburden” bandied about in sedimentary circles.