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JSW #3: Experimental Sedimentary Systems

February 7, 2007

This is the third post for the Just Science week (Feb 5th-9th). See Monday’s and Tuesday’s posts.

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On the first post for this week, I said I would stay within a theme of deep-marine sedimentation….well, i’m gonna break from that for this post just because the topic today is just that cool.

For a few years i’ve been following the work at the St. Anthony Falls Labratory, University of Minnesota, in Minneapolis. And a good friend of mine who works there was kind enough to give us a tour in December. This place does all sorts of cool stuff…like super-cavitation research (!)…but, here i’m gonna show you a few images from their experimental set-ups for studying sedimentation.

So, basically what we got here are some very sharp scientists who have taken ‘playing in a sandbox’ to the ultimate level. They have two main experimental tanks that interest me the most: a delta basin and the experimental Earthscape basin, or “Jurassic Tank”.

The above image is a deposit growing in the delta basin. Remember this is just a couple meters across. These experiments run for weeks and they photograph at equal time increments so they can make a time-lapse movie at the end to see the evolution of the system. But the real beauty of this is the quantitative information. At other increments during the run time, they scan the deposit with an extremely precise laser and collect data about the topography of the feature. As the deposit is buried by further deposition, they can relate this information to patterns of river avulsion and lobe-switching identified in natural systems.

The image to the right is a plan-view image from “Jurassic Tank”, which is an experimental basin a few meters wide by a few meters long. What makes it unique is its ability to create differential subsidence in almost any imaginable pattern. The “basement” of the basin is actually an interlocking framework of numerous plates that each move independently from each other. With this they can run experiments with similar subsidence patterns that are seen in Earth’s sedimentary basins.

And, like the delta basin, the progress of the filling is scrutinized and measured. At the end, the entire basin fill is carefully sliced centimeter by centimeter and high-res photos are taken of the cross-section. The goal is to then relate the explicit knowledge of the sedimentation to the resultant stratigraphy. In the “real world” we typically only have the stratigraphy remaining…and it’s up to geologists to interpret the processes that generated it.

These experiments are helping us think in different ways regarding what actually controls the patterns we observe and map in stratigraphy.

Check out their web resources:
– St. Anthony Falls Lab (SAFL), is part of
– National Center for Earth Surface Dynamics (NCED)
NCED Research Projects
– a link to some movies
data repository for the stratigraphy experiments

This short article from Science in 2000 does a much better job at explaining the goals of particular research projects utilizing these facilities (note: you’ll probably need a university or personal license to download).

Science 17 March 2000:
Vol. 287. no. 5460, pp. 1912 – 1915

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