Mystery Fossils Found Wintertime Lake Michigan Beach

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Winter 2010/2011

Most years, Lake Michigan’s wave action and chilling temperatures pushes ice and snow into huge mounds over the shoreline as high as twenty feet (shown above). In order to actually see the big lake you have to climb the mounds without falling in. Danger lurks around those edges where people can and have fallen through.

It’s January 2013 and the second consecutive season where the sand is left bare of winter’s icy layers; which I can’t stress enough how extremely rare that is. Looking towards the horizon over Lake Michigan, you would normally see a frozen tundra of stillness. Not this year. Compare the photo above taken winter 2010/2011 from the photo below taken winter 2012/2013.

Lake Michigan 2013

Lake Michigan Unfrozen January 2013

Case in point; due to the season’s whirling winds, minus the layers of snow, and less tourist traffic, fossils are more exposed from the continuous movement of sand. Below, are several interesting samples of fossils I found on Oval Beach, Saugatuck, MI (USA) winter 2012/2013. I haven’t been able to fully identify these species partly due to their smoothed surfaces, so please feel free to make suggestions. I have provided a few best guesses.

Coral Fossil, Geode or both?  Mystery Fossil 1

Coral with embedded crinoids

Crinoids embedded in coral or chunk of seafloor, Mystery Fossil 2

Fossil Coral

Sponge or Coral? Mystery Fossil 3

Fossil Coral

(reverse side of fossil above)

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Favosite and Rugose Corals Named after two Michigan Cities

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Southwest Michigan Oval Beach old pier pilings and rocks reveal low water levels in 2012

During the month of December, the ground is usually  covered with layers of snow here in Southwest Michigan (USA) and the big lake looks like a frozen tundra. Fossil exploring is usually put on hold till Spring, but 2012, so far, has shown to be a mild winter. As a result, the sand along the shores of Lake Michigan is more exposed to strong winds which has actually assisted fossil finding. The moving sands reveal hidden treasures one must partake while it lasts.

Below, are two recent discoveries of extinct corals found on Oval Beach in Michigan’s southwestern tourist town of Saugatuck. Although closely related and most common during the Silurian and Devonian time periods, the two corals derive from different orders by virtue of their skeletal growth patterns (tabulate and rugose) respectfully. Colonial building favosites are the most common form belonging to the tabulate group while the individual horn corals are probably the most well known among the rugose group. But don’t be fooled, the rugose order also included some colonial varieties.

Follow below as I define some of the characteristics of each order and try to guess for yourself which orders these two fossils fall under. Answer at the end.

The “tabulae” from the order tabulate refers to the horizontal internal partitions visible from a side view of a good specimen. Observe the diagram below of a favosite fossil. 

Rugose corals (named for their wrinkly outer skin) had less developed horizontal partitions, but stronger vertical ones. Most rugose corals have septae radiating from the center (like bicycle spokes) when observed in a cross section.

rugose-coral-morphology-diagram

 

Many tabulate corals can be associated with smaller honeycomb patterns of their corallite structures which housed the jelly-like polyp creatures. Whereas the rugose corals are often associated with larger more hexagonal patterns of their corallites.

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Southwester Michigan location of Saugatuck’s Oval Beach

The first Michigan fossil I found on Oval Beach in  southwestern Michigan is often referred to as the Petoskey Stone  “Hexagonaria, percarinata”  named after the northwestern city of  Petoskey, Michigan where they are commonly found. It’s  about the size of a fist and is rather smoothed out from water and sand action, yet it’s a nice large specimen that reveals the entire coral. From the side view, you can clearly see how it was attached to the seafloor by its stem.

 

 

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Petoskey Stone

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Side View of Petoskey Stone

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Details of Petoskey Stone Corallites

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Petoskey Stone, “Hexagonaria, percarinata” Rendering/Drawing

 

The other extinct Michigan coral fossil I found on Oval Beach is nicknamed the Charlevoix Stone. It’s smaller in total size, but is especially distinguished by its smaller honeycomb like corallite patterns.

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Charlevoix Stone

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Side view of Charlevoix Stone

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Charlevoix Stone “Favosite” Rendering/Drawing

The two Michigan cities of Petoskey and Charlevoix lie in close proximity to each other in the NW region of the lower peninsula. Yet, both cousin fossils can be found on the far southern shores of Lake Michigan’s coastline where I found my fossils south of Grand Rapids seen on the map.

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Petoskey and Charlevoix are far north of Saugatuck’s Oval Beach

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Petoskey and Charlevoix in close vicinity

 

 

 

 

 

 

 

 

 

So, if you haven’t already distinguish which order the Petoskey and Charlevoix Stones belong, I will tell you. The Petoskey belongs to the order of rugose and the Charlevoix is a favosite, (not yet determined which species) from the order of tabulate.

 

Recent Find (Halysite Coral)

Oval Beach in winter 2012

Oval Beach Saugatuck, Michigan  Winter 2012

I was super excited to discover some fossils on Oval Beach in Saugatuck, Michigan (USA) that are highly unusual to find this time of year (winter). The sample below is an extinct tabulate coral, a reef building colony type coral called halysite. We often find salt water fossils from the Paleozoic Era on our fresh water Lake Michigan shores. To explain this phenomenon I’ve written an article  entitled “I Found a Fossil on the Beach and Wondered” at hubpages.com where I’m also the fossillady. A link is provided in the box to the right.

This halysite coral is easy to distinguish due to the chain link appearance coining it with the common name “chain coral”. It was lying under layers of sand that aren’t usually exposed during the winter months. But with the mild winter (meaning no snow) the winds have push sand off the under layers. Also, due to low water levels from a long dry spell during summer 2012, there’s more beach to explore.

The extinct halysite corals displayed small tubes from which resided the jelly-like coral animals called polyps.  The coral polyps contained stinging cells for protection and also grasped plankton food that passed by in the ocean currents. As the corals grew, they built up walls of tube-like chambers called theca which steadily multiplied adding more links to the chain.  As they continued to multiply, they built large limestone reef structures on the seabed. They thrived mostly during the Silurian period up to 425 million years ago!

Classification

Kingdom: Animal

Phylum: Cnidaria (means stinging animal)

Class: Anthozoa (means flower animal)

Order:  Tabulata (possess inner horizontal dividing walls from growth patterns)

Family: Halisitidae (means chain coral)

Genus: Halysite  Species:unknown

Halysite Coral

Halysite Coral Fossil

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Halysite Colony “Chain Coral” Rendering