Dear Miroslav,

I am afraid it's just sandstone concrections - no fossils, sorry.

thomas

I also think that those are concrections, but I needed a second opinion.

Thank you very much.

Concretions the most probable !

If they are sandstones, then are concretions.

Varoujan

The first one is not. It is white, soft limestone-chalk.

The first one, if limestone, could be some kind of bivalve, not brachiopod, but imposible to determine. The second one, I also agree that seems concretions.

The first has the appearance of a thick-shelled bivalve, possibly an oyster, but the second does seem to be a concretion.

I agree, the second one looks like a concretion. The first one is uncertain, but I suspect that if it is a fossil, it is too poorly preserved to be identified.

In the  absence of structture, they are just concretions

 Unfortunately I feel that these are concretions.

I wouldn't rule out an organic origin for pictures 3, 4, 5 and 6. I find a very porous look as for they were concretions and, at time they have a peculiar arrangement (but not as nodules) . Why don’t see it as Ichnofossils? Perhaps some kind of burrows?

I agree the first has the appearance of a thick-shelled bivalve.

What is the likely environment of deposition of these upper Miocene sediments? If the nodules came from a distal shelf/ proximal slope setting they could be phosphorite nodules. If you cut them through the middle you may be able to see what it nucleated on.

The deposition environment are close to fluvial-lacustrine.

I am quite sure that these forms are not of biogenic origin and they are certainly no phosphorite nodules - those are typically darker and much harder.