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Paleozoic
Ordovician limestone (From same rock
layer in Ohio)
This specific fossil coral is found only in the
rock strata known as the Gravel Point
Formation. The Gravel Point Formation is part
of the Traverse Group of Devonian age. The
Gravel Point Formation is a mixture of
limestones and shales. The outcrops of these
rocks are restricted to the Little Traverse
Bay area near Petoskey. The Gravel Point
Formation is only part of the Devonian in
Michigan. Devonian age rocks form the
bedrock for much of the northern Lower
Peninsula. Devonian rocks outcrop at less than
three percent of the surface of the United
States. Michigan's average is much higher.
Much of what is known about the Devonian is
interpreted from the fossil record.
The most often asked question is, "What is a
Petoskey Stone?" A Petoskey is a fossil colonial
coral.
These corals lived in warm shallow seas that
covered Michigan during Devonian time, some
350 million
years ago.
Stromatolites of Michigan
Stromatolites are Formations built by Fossilized Algae. The Stromatolite Formation
shows the life processes of cyanobacteria(formerly called blue-green algae). The
primitive cells (Prokaryotic type), lived in huge masses that could form floating mats or
extensive reefs. Masses of cyanobacteria on the sea floor deposited calcium carbonate in
layers or domes. Most often, stromatolite Formations will appear as variously-sized
arches, spheres, or domes.
Kona Dolomite is a very ancient rock in which Fossil Stromatolite Formations (Blue-Green
Algae) from 2.1 to 2.2 Billion Years Old occur. The Fossil Stromatolite Formations were
built by some of the first life on earth, and are thought to have changed the atmosphere
to allow life as we know it today. Fossil Stromatolite Formations are found in the lower
eras of the Middle Precambrian Period. Stromatolites are abundant and are found in
many colors and shapes including Domes.
Kona Dolomite is not pure Dolomite as Silica is present which shades into Chert and
Quartzite. The strata has been subjected to many forces of nature including intense
folding, faulting, and shattering which often results in a breccia cemented with Quarts
and Hemetite.
Stromatolites were thought to have been extinct until forty years ago. However, with the
discovery of modern stromatolites in Shark Bay, Australia, and elsewhere, it is now
known that some are actually comprised of living cyanobacteria that grow on top of each
other at a rate of 1mm a year. These examples are sometimes called "living rocks."