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An End-of-Year Fossil Hunt with Stromatolites Galore


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Elasmohunter

What better way to celebrate the end of the year than with a little fossil hunting? And the hunt ended with some spectacular stromatolites; read on!

 

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When I got an itch to hit the field last month, I reached out to a quarry in Perrysburg, Ohio to collect fossil and mineralogical samples for donation to academic institutions. The quarry was kind enough to grant me permission to collect on their property for several hours in late December, so when the time came, I suited up and headed out with a trusty assistant.

 

The quarry exposed outcrops of the Lockport and Greenfield Dolomites separated by a thin lens of shale. We were permitted to collect from the outsides of the berm piles surrounding the walls, but I wasn't sure what to expect, as dolomites often exhibit poor fossil preservation, and I had never hunted these units before. Even so, we eagerly hit the berm piles with rock hammers in hand.

 

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The quarry wall. The Greenfield Dolomite (red line) sits on top of the Lockport Dolomite (blue arrow), which extends to much deeper than the shelf upon which the photo was taken. The shale horizon between them can be clearly seen as a dark line.

 

Almost immediately, I found a small brachiopod, but then it was several more minutes before we found other fossils. We proceeded to find a variety of reef-building organisms.

 

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A small brachiopod (1) and . . . the underside of a Favositid coral (2)?

 

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A friend suggested that the larger of these two fossils (3) is a Favositid coral. I'm not sure about the smaller one (4); maybe a bryozoan?

 

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This find (5) confused me: it looked like a concretion, seemed to be covered in iron oxide, and had an odd, striped/fluted pattern inside. A friend suggested that it could be slickenslides. It was the only rock that I saw that looked anything like this, and it really stood out against the dolomite.

 

The best finds of the day, however, were undoubtedly the stromatolites. The quarry exhibited them in abundance, and they were readily found throughout the berm piles.

 

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The rounded tops of a group of stromatolites.

 

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The mottled top of a stromatolite. More layers can be seen just above the left side of the rock hammer.

 

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Check out this stromatolite (6)! The coin on it is an American penny. It came from a stromatolite that seemed to be at least 60 or 70 cm in diameter.

 

Not only did we find fossils, however; we also found several crystals, as the dolomites were scattered throughout with crystal-containing vugs.

 

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Here's the largest crystal that we found. I haven't tested it with acid, but I suspect that it's calcite. We collected a few other crystals too and even saw some purple ones hiding in a seam in a large boulder.

 

Unfortunately, someone beat me in discovering stromatolites here by many decades, so I didn't make an groundbreaking discoveries, but the trip was nevertheless a wonderful way to round out the year, and all of these samples will end up in academic institutions.

 

May you all have even better fossil hunts in the new year!

 

Cheers,

Elasmohunter

 

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Elasmohunter
4 hours ago, Yoda said:

Fantastic Stromatolites :envy:

Many thanks! :yay-smiley-1:

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