Stromatolites from Steep Rock Lake

The Steep Rock Lake Limestone from northwestern Ontario, west of Lake Superior, is a stromatolitic limestone of Archean age (~2.9 billion years old).  Stromatolites are calcareous structures created by cyanobacteria (blue-green algae).  The photos below are of a specimen of the limestone that was cut into a thin slice approximately 1.5 mm thick.   The photos were taken with a low power microscope.  The fields of view are approximate.  The black specks in the photos are small hunks of carbon.  I speculate that the greenish gray blobs are original algal structures.  Note that the color in the photomicrographs is greener than the actual specimen.  The whole slab picture below gives a better indication of the specimen color. Also note that jpeg compression has introduced some artifacts into the images.  I can provide copies of the original tiff images via emial to anyone who is interested.  I would like to find someone with the proper equipment to search this specimen for fossil cell structures.
 Field of View: 5mm  Field of View: 2.5mm Field of View: 2.5mm  Field of View: 1.5mm


Below is a view of the whole specimen. The wavy pattern is characteristic of stromatolites.

Field of View: 25cm

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All images ©1999 Daniel Moore