Kelp? Pseudofossil?

[Tachikoma_kun]

As above, I showed these pictures in a post asking how to prep the mudstone, but before I get cracking (so to speak) I was wondering if these are even fossils or just mineral stains. I have looked for Lyme Regis (Black Ven - 160 MYO-ish) fossils, but the touristy nature of the place doesn't help with Google searches.

I think it's some sort of kelp, I found lots of similar inclusions, but they are all so badly preserved (if indeed they are fossils) that there's not a lot of detail to identify if it's a plant, worm, fish or feather (I wish lol).

Thanks for looking.

Scale CM/MM

[Indy]

I'll "break the ice"

I'm wondering what leads you to believe the

shape or features might point to "fossil Kelp"

[Bullsnake]

Looks like a cross section of something. Maybe a brachiopod(?)

[Tachikoma_kun]

Good question Indy, I found quote a few like this, sime of them were a good 12" long and lying perfectly along the layers with trillobites and bivalves, so definitely marine. I don't think its a worm, and this specimen has a very leafy shape compared to the others I found. The "fossil" from the mudstone thread appears to have chambers or bladders similar to modern kelp/seaweed running along its length, but I didn't copy that photo here as it still needs prepping. Its pure speculation as I can't find any information about marine plant fossils from the area. I'm more inclined to think its just some sort of stain, but thought I would check here.

I don't think its a cross section of something as it has no depth, it only seems to exist in-between one layer of the mudstone.

Thanks both :-)

[TqB]

It's probably a compressed burrow, something like the ichnogenus Planolites which occurs in various beds in the area.

[Tachikoma_kun]

Interesting, thanks TqB!

I think that would be more interesting if it's right, what would explain the outline though? I found some of these both with and without the "leafy" outline,.

[TqB]

The "leafy outline" is a mineral halo rather than part of the fossil, not sure how they're caused but it looks like a sort of chromatographic effect, something to do with pyrite - perhaps someone here knows?

[Terry Dactyll]

I think a 'mineral halo' is a brilliant description of what happened...I reckon when the plant fragment or whatever was first buried I presume it was in a very damp solid solution of mud for a while where the surface of the item would be kept wet...some of the colour/minerals leached from it into the mud immediately around it and then the nodule forming process initiated... the minerals leached out from the fragment and started to change the grains around and the sphere of influence of these minerals is defined by the shape of the 'mineral halo'...Ive seen this colour variation caused by minerals and fossilisation in mudstone previously on partly formed plant fossils but the boudary of the sphere of influence was not as well defined...

a partly formed nodule where the mineral content of the mudstone wasnt quite right to complete the process of nodule formation...

[Wrangellian]

Good explanation re: mineral halo, guys, I'll remember that term

I'm wondering if the object could be a coprolite from something..?

[Maniraptoran]

Planolites, huh? a month ago i found a lot fossils like that in some big landscaping rocks (made of chalk/chert, i think). hear are some pics in anyone is interested:

[Tachikoma_kun]

Haha, I love the variation in opinions, just argue it out between yourselves and I will label it when you have finished!

Any idea what they are Mani? seems the worm burrow idea is pretty close to what I found.

[Indy]

Haha, I love the variation in opinions, just argue it out between yourselves and I will label it when you have finished!

Speculation is fun but positive ID comes with known references.

When dealing with specimens like you posted...Many times a "best guess" is

what one ends up with.

PS: Almost everything is identifiable depending on the amount of time

and energy one is willing to spend going on a quest coupled with those

willing to research the literature for references. As far as I'm concerned...

I will join you and follow the thread to to see if a positive ID is

forthcoming or we end up with the best possible guess

.

Edited September 29, 2011 by Indy

[Tachikoma_kun]

Whatever it does turn out to be, I will be happy if it's a worm tube, coprolite, anything, even though it's not a very striking fossil it's still something new for my collection.