Last week's Fossil Friday was a beachcomber's delight. According to our fossil friend Gerald Wilgus, these fossils apparently wash up on Lake Michigan to this day.
What is it? Well, I’ll let Gerald supply the answer:
“Petoskey stones are sought after by beach combers and are the remains of Hexogonaria percarinata colonies deposited during the Devonian on the reefs in the Michigan Basin. Glaciation ripped into those reefs to break apart some of the Hexogonaria percarinata colonies, rounding off the chunks and depositing them in the lateral moraines of Northwest Michigan.
I frequently find Petoskey Stones when I stop along beaches while sea kayaking on Lake Michigan.”
Here is a little more detail from Michigan State University:
“So, what is a Petoskey stone? It is a fossil colonial coral that lived in the warm Michigan seas during the Devonian time around 350 million years ago. The name Hexagonaria (meaning six sides) percarinata was designated by Dr. Edwin Stumm in 1969 because of his extensive knowledge of fossils. This type of fossil is found only in the rock strata called the Gravel Point Formation. This formation is part of the Traverse Group of the Devonian Age.
During the Devonian time, Michigan was quite different. Geographically, what is now Michigan was near the equator. A warm shallow sea covered the State. This warm, sunny sea was an ideal habitat for marine life. A Devonian reef had sheltered clams, cephalopods, corals, crinoids, trilobites, fish, and many other life forms.”
