ID: Plant or dendrites?

[Max-fossils]

Hi all!

 

Found two stones last summer in Aubrac, France. I found them in between many other stones in a property near Laguiole. I have no clue of the age of the fossils.

When I picked them up I was pretty sure they were fossil plants, but now I'm starting to think a bit differently. I'm starting to think that the first stone has dendrites; but for the second I can't make out anything.

What are your opinions?

 

Best regards,

 

Max

[Max-fossils]

[Max-fossils]

The 4 previous photos are all from the same stone, just different areas of it. Are they all dendrites/ all plants or a mix of both? Some look very different to others; that's the thing that's puzzling me the most.

 

Next 2 photos really confuse me. What could they be?

[marguy]

Hello Max,

I think you do not have any fossils here, only pyrolusite dendrites (manganese oxide)

Some dendrites are very fine and other deposits are coarser, which is the case on  the second stone.

Marguy

[ynot]

I agree with marguy. They are dendrites. They can build up to the point that they are a solid layer covering the rock.

[abyssunder]

Unfortunately, I'm not familiar with the region and the possible fossils, but, I propose these:

1 - Maybe the rocks are dendritic tufa.
2 - There is a similarity with *Microbialites .

 

a, b, Modern microbialite microstructure; c, ancient carbonate deposit. a, SEM shows individual bushes of calcified filamentous microfossils and trapped sediment. Authigenically calcified picoplankton comprise calcareous sediment matrix. SEM specimens were impregnated in expoxy resin, etched in 2M HCl, and Ir coated. b, Branches of dendrite consist of radiating splays of larger calcified filaments, supported by a framework of thinner calcified filaments, calcified extracellular matrix, and trapped and bound sediment particles. c, Optical thin section shows dendritic fabric of potential ancient analogue Epiphyton. In the early Cambrian Shady dolomite of southwest Virginia⁵, Epiphyton forms mound-like structures similar to the large mounds found in Pavilion Lake.  from here

 

" Microbialites are in place benthic sediments produced by microbial processes. The term “microbialite” has been most widely used to describe carbonate stromatolites,
thrombolites, and similar structures that occur as domes and columns in the shallow waters of lakes and seas, but it can also apply to many additional authigenic accumulations in which microbes are locally conspicuous, such as some tufa, travertine, speleothem and spring, seep, and vent deposits. A series of terms and definitions were proposed between 1967 and 1987 in attempts to distinguish benthic sediments formed by microbial sediment trapping and/or precipitation. " - *

 

 

 

[Max-fossils]

15 hours ago, marguy said:

Hello Max,

I think you do not have any fossils here, only pyrolusite dendrites (manganese oxide)

Some dendrites are very fine and other deposits are coarser, which is the case on  the second stone.

Marguy

 

15 hours ago, ynot said:

I agree with marguy. They are dendrites. They can build up to the point that they are a solid layer covering the rock.

 

14 hours ago, abyssunder said:

Unfortunately, I'm not familiar with the region and the possible fossils, but, I propose these:

1 - Maybe the rocks are dendritic tufa.
2 - There is a similarity with *Microbialites .

 

a, b, Modern microbialite microstructure; c, ancient carbonate deposit. a, SEM shows individual bushes of calcified filamentous microfossils and trapped sediment. Authigenically calcified picoplankton comprise calcareous sediment matrix. SEM specimens were impregnated in expoxy resin, etched in 2M HCl, and Ir coated. b, Branches of dendrite consist of radiating splays of larger calcified filaments, supported by a framework of thinner calcified filaments, calcified extracellular matrix, and trapped and bound sediment particles. c, Optical thin section shows dendritic fabric of potential ancient analogue Epiphyton. In the early Cambrian Shady dolomite of southwest Virginia⁵, Epiphyton forms mound-like structures similar to the large mounds found in Pavilion Lake.  from here

 

" Microbialites are in place benthic sediments produced by microbial processes. The term “microbialite” has been most widely used to describe carbonate stromatolites,
thrombolites, and similar structures that occur as domes and columns in the shallow waters of lakes and seas, but it can also apply to many additional authigenic accumulations in which microbes are locally conspicuous, such as some tufa, travertine, speleothem and spring, seep, and vent deposits. A series of terms and definitions were proposed between 1967 and 1987 in attempts to distinguish benthic sediments formed by microbial sediment trapping and/or precipitation. " - *

 

 

 

Alright, thanks all!

Kind of a deception to find out they aren't fossils

But at least now I know!

 

Best regards,

 

Max