 This
stromatolite is from the Gunflint Formation, a Paleoproterozoic
chemical-clastic sedimentary assemblage outcropping to the immediate
northwest of Lake Superior that became famous in 1954 for containing
the oldest fossil assemblage known at that time. Older microfossils
have since been discovered, but the Gunflint prokaryotes remain
one of the most diverse Precambrian fossil communities. In the March
7, 2002 issue of Nature (Volume 406), J.W. Schopf, famous for his
role in the discovery of Domain of Life Archaea, reported discovery
of cellular remains of prokaryotic cells in the Gunflint stromatolites
(combining optically discernible morphology with analyses of chemical
composition using laser-Raman spectroscopic imagery). His results
remain controversial, however. At about the same time, the age was
measured at 1.9 billion years. Notice the veins of fool's gold in
the specimen.
Barghoorn, E.S. and Tyler, S.A., 1965: Microorganisms
from the Gunflint Chert. Science, vol. 147, p. 563-577.
Schopf, J.W., 1999: Cradle of Life: The Discovery of Earth's Earliest
Fossils. Princeton University Press.
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