Friday, March 22, 2013

Screening the Arkona shale for microfossils

I ran a sample of the Arkona shale through my screen set to see what I could find. I didn't look too long or closely as this was meant to be a dry run or proof of concept test.

This is the rock sample that I used. Note the Phacops fossil, you'll see more of it later.

The Arkona formation is mostly clay and readily breaks down when in contact with water. In preparation for this experiment I left the chunk of matrix in some water for 24 hours to let it completely break down.

It took about a hour to get all the screening completed, the biggest obstacle is that the water will become saturated with clay while washing and needs to be replaced. So far it has been much cleaner and easier to do all the screening outside with a bucket of clean water to occasionally rinse the screens through.

Here are the results. From the #35 screen I found at least two species of Ostracod, lots of Tentaculite pieces and bits of the Trilobite that disintegrated while the clay matrix broke down.

The #60 screen had smaller bits and pieces (as is to be expected) along with some possible Ostracods but nothing that I was able to easily pick out and ID...

A Styliolinid...
Part of a Conodont/Scolecodont....
And other stuff.

Now we are getting to the really tiny stuff. The #120 screen material looked like this:

 and the #230 screen material looked like this:

I took all the above photo's with my Zorb digital microscope but that only magnifies to 20X. To see anything meaningful in the #120 and #230 screens I would need a real microscope.

So the experiment was a success and I've learned a bit about how to best screen samples of clay matrix material. My next experiment will be with eroded Silica Shale from the dump piles near Sylvania, Ohio. The step after that will be to figure out the best way to separate the tiny samples for the fossils I want, ID what I find and then store them so they don't get lost.

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