Beechwood Limestone, Upper/Middle Devonian, Indiana, 388 million years old.
Here are the links to previous microfossil samples.
Close-up on conodonts from Grassy Creek Shale, Missouri: " • Close-up on conodonts ... "
Conodonts. Brief story of a microfossil: " • Hunting for Conodonts.... "
Discovering micro world of fossils: " • How to study fossils u... "
Fossilized gastropods from Stone City Formation, Texas, Eocene:
" • Fossilized gastropods ... "
Permian sharks and reptile fossilized teeth from Waurika, Oklahoma: " • Enigmatic Permian shar... "
It seems like this gelatin capsule from our collection of microfossils is our best so far. We found plenty of conodonds of various shapes and colorations. There are pointy conodonts and those that look like leaves. Some of them are pale brown and translucent, the others have vivid reddish hues and they all are spectacular. In previous episodes we discussed the possible origins of conodonts and their color index reflecting changes in color depending on the temperature the fossils were subjected to deep under the Earth surface. However, the heterogeneous mix we see here may be an example where the color is defined not only by the temperature but also by the mineral content of the matrix surrounding the fossils. The red color is often the result of the presence of iron oxides.
The geological formation called Beechwood Limestone member was given its name early last century. It was a crinoidal limestone deposit discovered near Beechwood Station of Louisville in Kentucky. According to the label provided by the vendor, our sample comes from Speed, Indiana. This is one of designated reference sections along with the one in Louisville in Kentucky and other two in Indiana at North Vernon and Elizabethtown.
In addition to conodonts, the Beechwood limestone contains glauconite and macrofossils like bivalves, bryozoans, brachiopods and crinoids. Despite the variety of forms, most of the conodonts we see here belong to one genus called Polygnathus. Conodonts occur in so-called assemblages or certain combinations of several and often very different forms of dentitions. This is what Geologists call Polygnathus varcus Zone corresponding to Givetian subdivision of Devonian period, approximately 388 million years ago plus-minus 3 million years. By that time jawless fishes started to decline giving a way to jawed fishes the very lineage that will eventually lead to appearance of lung fish crawling out of water to concur the land.
By the way, limestone is a popular building material in Indiana starting from the early days of Pioneers. It is a fireproof material and suited well for urban architecture. Next time you see Empire state building, US National Cathedral in Washington DC or the Pentagon thing about Indiana limestone and the fact that it contains remnants of organisms lived million years ago. To be fair, the Indiana limestone can be of different periods, for instance Mississippian limestone is of good quality material, but I’m convinced that somewhere in building blocks, lay hidden and invisible by naked eye … conodonts.
Thanks for watching and good luck on your fossil-searching trips!
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Негізгі бет Microfossil sample #5. Best conodonts so far.
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