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Dextral and sinistral and forams, oh my!!
Submitted by Malinda Burk on Tue, 06/30/2009 - 21:26
In between quick trips to the TV to watch the dynamic positioning folks try to get the drill pipe inserted, we had a great lesson from Leslie S. on foraminifera. These little guys (well, I guess some could be gals...) are tiny one-celled protists that create calcium carbonate tests (aka shells) that have one or more chambers.
In particular, we learned about planktonic forams; they are mostly found closer to the surface of the ocean, and stay above the thermocline.
Yesterday, we took 20 cc samples of different cores; specifically 1020B and 1014A. We bagged and tagged the samples, and then washed the 1014A sample using a fine screen and plenty of water.
Our mission for today was to separate our washed and dried samples using very fine screens like the ones below:
We sorted the samples into 4 different sizes: <150 microns, 150-250 microns, 250-355 microns, and >350 microns. We made special sample slides out of each size and then went to the microscope to see what the sample contained. In particular, we were interested in the 150-250 micron size sample. Here are some typical forams one might see:
Our goal was to find 20 Neogloboquadrina pachyderma forams AND figure out if they were dextral or sinistral (which direction they were coiled). Here's the difference:
You can tell the difference by finding the smallest chamber and following it around to the biggest chamber. So our foram on the left is dextral and the one on the right is sinistral.
So why do we care about these little critters? Well, they can provide a current and historical record of temperature changes. Different types of foraminifera appear at different times of the year. The dextral and sinistral shape also provide a clue into temperature variations.
Stay tuned for results from our core samples!