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Preservation in species-specific color

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Does anyone know of deposits other than the LeGrand crinoids where each species is preserved in a different characteristic color, all on the same slab? We have this kind of thing in the brachiopods and trilobites of the Decorah Formation (Late Ordovician) here in Missouri, which is what got me thinking about it. But I've never seen a report summarizing other cases of this phenomenon, and as I think about it I'm not sure I can name any others. Can you?


Brachiopod photo info:
A= Zygospira
B= Rafinesquina
C= Doleroides
1 = Isotelus, rusty brown
2 = ?Achatella, light gray.

Highway M near Antonia, Jefferson County
Decorah Formation, Late Ordovician, ~450 million years old


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My (uneducated) guess would be that since each species has a slightly different cell structure that the size and composition of the crystals that replaced them during permineralisation is slightly different, lending them their different colours.

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If it were as simple as that, then we would see such color differentiation within a single bed on a regular basis. Instead, it seems to be the rare exception.


That said, I'm less interested in guessing at the mechanism and more interested in gathering cases.

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