Help ID

[Dimitar]

I found this specimen in Laval, on the South shore, West side. There was a fall there, next to the river  there is a mixture of different layers. 

The time should be after Ordovician or late Ordovician.   The rock is black, on very thin flat layers. Some layers are very hard / silicates/ other are fragile, mud - coal .   Initially I expected it to be nautiloid. But when I did the pictures I rejected it.

 

 

 

 

1. Both parts

 

 

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4. Side view - both parts

 

5. Cleaned (lower part)

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Edited June 5, 2021 by Dimitar

[Dimitar]

12. Transverse view

13 . Other small fossils in the upper side on the reverse plate

Edited June 5, 2021 by Dimitar

[Tidgy's Dad]

Squished nautiloid for me. 

[Dimitar]

There are nautiloids in the same rocks. Here is another example, a lot better visible:

 

 

 

 

 

Edited June 5, 2021 by Dimitar

[Kane]

Orthoconic nautiloids commonly appear in the upper Ordovician shales as compressed due to pressure from preservation. The colour is on account of pyrite from available sulfides in the initial mud allowing for mineral replacement. There will be no coal in these formations, as coalification mostly occurred during the Carboniferous.

[Dimitar]

Great answers! Thanks a lot Tidgy's Dad and Kane .