Looking at forams!

Hi crew: Yesterday we saw the tiny calcareous nannofossils that makeup the major portion of calcareous ooze. These phytoplankton are so small you can’t even see them with your naked eye, yet they accumulate to great thickness in the deep-sea. Not all the microfossils are so small.

The critters I study (planktic foraminifera) are also single-celled protists, but they are sand-sized. We can study ‘forams’ with a reflected light binocular microscope rather than a high-powered petrographic microscope. Today’s picture shows a core-catcher sample brought to the paleo lab for processing. I’m shown here washing the calcareous ooze over a 63 micron screen/sieve (= 0.063 mm); this size fraction corresponds to the boundary between sand-sized particles and silt and clay-sized particles.

The forams are caught on the sieve while the calcareous nannofossils pass through and are washed down the sink. You can see there are a lot of forams in these samples. I’ll show you what they look like during lab in the coming weeks. I’ve also included some Scanning Electron Microscope images of some of the foram species I identified in the samples from Ontong Java Plateau. All 4 of these species are good index fossils (i.e., good age indicators). Talk with you tomorrow! Mark L.