Carbonized preservation from precambrian?

[Mahnmut]

Hello together,

I just got a fossil that I am not sure what to make of. The species ID I got is Nemiana/Beltanelliformis, which I have no reason to doubt so far.

https://en.wikipedia.org/wiki/Beltanelliformis

What has me wondering is the preservation. Most pieces the seller had to offer seem to be imprints or remnants of sediment glued together by biofilms as one would expect for the species, like in the third pic. Containing mica interestingly.

The piece in question appears covered in a shiny black layer that reminds me very much of what I once found in a glass bottle of coke that had melted in a campfire, turning its sugary content into coal.

In case of the fossil it may be other dark minerals of course, but after reading about organically preserved specimens I dared hope that it may be the actual carbon.

What do you think?

Thanks

J

[Rockwood]

Well, along with iron and manganese it would be a top contender. Got a laboratory ? 

[Mahnmut]

Hi Rockwood,

well, not really a lab. More like a kitchen. Exactly like a kitchen in fact. And a balcony. But I can get some HCl, which should react with manganese (most probably MnO2 and/or other oxides) releasing chlorine( balcony it is). Carbon should be unimpressed by HCl. Under an oxidising flame on the other hand, metal oxides should not do much, while carbon would burn away.

I will wait if there are other hints though before taking samples of my precious fossil.

Cheers,

J

[Rockwood]

25 minutes ago, Mahnmut said:

while carbon would burn away.

But how would you tell ? If the answer is it would be gone the next question would be how it got to be on the surface and not incorporated into the rock.

[Mahnmut]

The black layer is definitely very thin, underneath it looks just like the specimen in the third picture.

So if it was indeed carbon, I would expect to be left with a brighter crumb of stone after exposing it to an oxygen rich flame.

As far as I understood Beltanelliformis it is supposed do be some kind of cyanobacteria colony incorporating sediment.

How much organic matter to expect inside one of the "pancakes" I do not know, maybe someone on the forum can enlighten me on that matter.

The chances of it being manganese oxide are rising though, first because ukraine, where this fossil comes from does have much of it, second because as far as I found out so far it is theorized that the oxidizing conditions that are necessary for the precipitation of Mn from solution may be related to presence of cyanobacteria amongst others.

this article concentrates on newly discovered earlier variants, but assumes that the cyanobacteria-flavoured variant is the standard if I understand it correctly:

https://www.pnas.org/content/110/28/11238

[Plax]

Phosphatic coating? If this was a hardground at some point this would be a possibility.

[Rockwood]

4 hours ago, Mahnmut said:

I just got a fossil

Can you be sure it was pristine at the time ?

[Rhiguita]

Ediacaran fossils are sometimes preserved under layers of volcanic ash, such as in Ukraine and mistaken Point Canada, which could explain the black layer.