Carboniferous Sphere

[Omnomosaurus]

One from the collection of specimens gathered about 4/5 years ago. I can't seem to find anything that might be a good candidate, so I throw it out to the wisdom of you guys.

 

Small rock from a Carboniferous Duckmantian deposit.

 

Locality: North Wales, UK

 

Appears to be a collection of plant material. Also present are small possible pieces of brachiopods/bivalve shell and this small spherical object (there is also a possible smaller secondary one above the larger).

 

It is very polished/shiny compared to the surrounding matrix and seems to be almost perfectly round, judging from the exposed portion. Any clues as to what the spherical object may be?

 

 

Thanks!

[Wrangellian]

Interesting. I do see 2 of those spheres there. I'll have to defer to the Carb experts, and will follow to see what they say.

[FranzBernhard]

Strange, indeed! Thanks for sharing!

Looks like some kind of breccia, first thought was some kind of concrete . I can not discern any plant parts with certainty.

The smaller one of the round and shiny objects seems to have a raised median line (between the arrows). Is this correct?

How did you find it, what else was there and what is the general geology of this stratum, @Omnomosaurus?
Franz Bernhard

 

[TqB]

They could be goniatites, either juveniles or nuclei - especially as you have other marine debris in there. The raised median line mentioned by @FranzBernhard is typical of a broken out nucleus.

 

Here's one in a broken cross section (Brigantian, Co. Durham):

 

For scale - the nucleus here is about 1mm across but can stay near spherical at later stages.

 

[Omnomosaurus]

7 hours ago, FranzBernhard said:

Strange, indeed! Thanks for sharing!

Looks like some kind of breccia, first thought was some kind of concrete . I can not discern any plant parts with certainty.

The smaller one of the round and shiny objects seems to have a raised median line (between the arrows). Is this correct?

How did you find it, what else was there and what is the general geology of this stratum, @Omnomosaurus?
Franz Bernhard

 

 

Haha, definitely not concrete; the rock is very lightweight. Though it wouldn't be the first time I'd picked up something completely useless. 

 

Good eye on the raised median line of the smaller object, I hadn't even noticed that!!

 

It was found in a rubble pile amongst lots of extremely well preserved Carboniferous plant material, including Calamites trunks, stigmaria & a variety of leaves, plus the occasional brachiopod (the fossil bed has been partly overturned & bulldozed to build a road).

 

Here is a random selection of plant material I have found from this same site (including this rock):

 

 

And this is the largest single jumble of brachiopods I have found there:

 

 

Shrimp fossils and a single trilobite have also been found in siderite nodules from another part of the same site (not by me).

 

 

1 hour ago, TqB said:

They could be goniatites, either juveniles or nuclei - especially as you have other marine debris in there. The raised median line mentioned by @FranzBernhard is typical of a broken out nucleus.

 

Here's one in a broken cross section (Brigantian, Co. Durham):

 

For scale - the nucleus here is about 1mm across but can stay near spherical at later stages.

 

 

Ooh, that could be it, actually! The colouration is even quite similar.

 

To my knowledge, no ammonoid remains have been found at the site to date, so this would be a turn-up for the books.

[FranzBernhard]

Thanks for all the infos, @Omnomosaurus!

32 minutes ago, Omnomosaurus said:

the rock is very lightweight

Strange!

32 minutes ago, Omnomosaurus said:

It was found in a rubble pile amongst lots of extremely well preserved Carboniferous plant material, including Calamites trunks, stigmaria & a variety of leaves, plus the occasional brachiopod (the fossil bed has been partly overturned & bulldozed to build a road).

The rock looks totally out of place! Was it one of a kind find?  Maybe it was brought in during road construction? I am still not convinced, that it is natural.

Btw, the plant fossils are very nice, congrats!

Franz Bernhard

[Omnomosaurus]

3 minutes ago, FranzBernhard said:

Thanks for all the infos, @Omnomosaurus!

Strange!

The rock looks totally out of place! Was it one of a kind find?  Maybe it was brought in during road construction? I am still not convinced, that it is natural.

Btw, the plant fossils are very nice, congrats!

Franz Bernhard

 

Thanks, Franz!

 

I don't think it was from the construction work, as there is no other foreign material in the rubble pile (there is fossiliferous limestone material from the road construction situated a short walk away).

 

There is however a lot of volcanic material, including large quartz crystals & obsidian commonly found for miles around the local area. Since the rock in question appears quite porous & lightweight, I have wondered if it could be volcanic in nature?

 

I believe this is the exact geological layout of the site (before partial bulldozing):

 

[Manticocerasman]

+1 for goniatite 

[TqB]

37 minutes ago, Omnomosaurus said:

There is however a lot of volcanic material, including large quartz crystals & obsidian commonly found for miles around the local area. Since the rock in question appears quite porous & lightweight, I have wondered if it could be volcanic in nature?

I'm wondering if it's actually industrial slag - you sometimes get charcoal fragments in it and the spheres could be condensation spherules of furnace glass .

 

You don't get obsidian in the UK (the nearest thing to it is probably pitchstone, most famously from Arran) but glassy iron slag can be indistinguishable from it.

[FranzBernhard]

Now the plot seems to thicken, @Omnomosaurus !

30 minutes ago, Omnomosaurus said:

There is however a lot of volcanic material, including large quartz crystals & obsidian commonly found for miles around the local area. Since the rock in question appears quite porous & lightweight, I have wondered if it could be volcanic in nature?

How old are these volcanics?  Are they part of the Carboniferous strata or younger? And yes, your rock could be a volcanic breccia or a volcanic tuff .

@TqB, oh yes, the man-made hypothesis is still there!

Franz Bernhard

[ynot]

35 minutes ago, Omnomosaurus said:

a lot of volcanic material, including large quartz crystals & obsidian commonly found for miles around the local area.

Quartz crystals are not typical of volcanic rock. Obsidian will completely decompose in 70 to 80 million years so there is no obsidian in the age rock You said the site contains.

[Omnomosaurus]

39 minutes ago, TqB said:

I'm wondering if it's actually industrial slag - you sometimes get charcoal fragments in it and the spheres could be furnace glass .

 

You don't get obsidian in the UK (the nearest thing to it is probably pitchstone, most famously from Arran) but glassy iron slag can be indistinguishable from it.

 

It's entirely possible that's what this is, especially with an 18th Century metalworks and evidence of coal mining dating back to medieval times in the area!

 

I had no idea about obsidian/iron slag! I always just assumed it was obsidian, due to the plentiful quartz and basalt found in the same vicinity. Here's a random piece that I have in a box:

 

 

36 minutes ago, FranzBernhard said:

Now the plot seems to thicken, @Omnomosaurus !

How old are these volcanics?  Are they part of the Carboniferous strata or younger? And yes, your rock could be a volcanic breccia or a volcanic tuff .

@TqB, oh yes, the man-made hypothesis is still there!

Franz Bernhard

 

I haven't been able to find info on volcanic activity in this area, but I would assume it to be part of (or prior to) the Carboniferous strata, as the preservation of fossils is too fine to have been subjected to extreme geological processes.

 

It could well be volcanic breccia or tuff!

 

Here are some more close-up photos:

 

[Omnomosaurus]

36 minutes ago, ynot said:

Quartz crystals are not typical of volcanic rock. Obsidian will completely decompose in 70 to 80 million years so there is no obsidian in the age rock You said the site contains.

 

Well, you learn something new everyday; thanks ynot!

 

The "obsidian" (which might be pitchstone, by the sounds of things) is located scattered across a wide area, including the vicinity of the fossil bed, but I haven't actually found any of it mixed in with the fossiliferous material.

 

Sorry if I didn't make that clear.

 

I'm not insinuating that this is definitely a volcanic piece, just trying my best to give an overview of the materials found surrounding the Carboniferous deposits, in case it has been mixed in from the surrounding area.

 

TqB might be into something with the industrial slag, but I've highlighted a couple of inclusions that look to be shell fragments; especially the one circled in red (same piece in all pictures), as it has a hollow tubular shape, from what I can see:

 

[ynot]

It could be cement that has some fossils that were in the gravel used to mix it. (?)

[FranzBernhard]

@Omnomosaurus, you are making my day!

34 minutes ago, Omnomosaurus said:

 

I am unable to decide, if this is obsidian, slag or some other kind of glassy material. I am noticing the transparency. Arrrgh!! (But its some kind of glass, probably). Other opinions?

 

34 minutes ago, Omnomosaurus said:

I haven't been able to find info on volcanic activity in this area

Ok, than there is probably none there. It should have been documented somewhere in a highly explored country like Wales.

 

34 minutes ago, Omnomosaurus said:

I would assume it to be part of (or prior to) the Carboniferous strata,

Yes, there are Precambrian and Ordovician volcanics in Wales. But this rock does just not look that old (porosity!).

Does the matrix of your rock fizz with vinegar or hydrochloric acid? Put a small fragment in acid; a drop of acid on this porous rock could be inconclusive.

 

34 minutes ago, Omnomosaurus said:

as the preservation of fossils is too fine to have been subjected to extreme geological processes.

Volcanism does not always rule out good preservation of fossils.

In this locality, the fossiliferous marl is directly overlain by an basaltic extrusion. The heat shock helped to preserve colour patterns in conus snails etc.

http://www.thefossilforum.com/index.php?/topic/73610-weitendorf-styria-austria/&tab=comments#comment-775203

 

So, the mystery remains!
Franz Bernhard

 

[TqB]

I'm sure your "obsidian" is iron slag - visually identical but easy to tell the difference in the UK as obsidian is not an option (unless someone dropped it!).

 

I find loads around where I live in NE England, plenty of black but other colours are common too - here's a selection:

[Omnomosaurus]

4 hours ago, ynot said:

It could be cement that has some fossils that were in the gravel used to mix it. (?)

 

It feels too light for cement to me, but it's always a possibility!

 

4 hours ago, FranzBernhard said:

@Omnomosaurus, you are making my day!

I am unable to decide, if this is obsidian, slag or some other kind of glassy material. I am noticing the transparency. Arrrgh!! (But its some kind of glass, probably). Other opinions?

 

Ok, than there is probably none there. It should have been documented somewhere in a highly explored country like Wales.

 

Yes, there are Precambrian and Ordovician volcanics in Wales. But this rock does just not look that old (porosity!).

Does the matrix of your rock fizz with vinegar or hydrochloric acid? Put a small fragment in acid; a drop of acid on this porous rock could be inconclusive.

 

Volcanism does not always rule out good preservation of fossils.

In this locality, the fossiliferous marl is directly overlain by an basaltic extrusion. The heat shock helped to preserve colour patterns in conus snails etc.

http://www.thefossilforum.com/index.php?/topic/73610-weitendorf-styria-austria/&tab=comments#comment-775203

 

So, the mystery remains!
Franz Bernhard

 

 

Ha wow, that's some interesting stuff @FranzBernhard!

 

I guess I've been mistaken all these years over volcanicity in the area. It was something I just assumed from the assortment of rocks & minerals around....guess I didn't pay enough attention in geology lectures! 

 

I'll see if I can find some vinegar and do a fizz test on a piece of the rock.

 

It's very sad about that site in Austria. The main site connected to where I collected this fossil is now protected, and has finally been fenced off from people doing the same thing, but there are many fossils left exposed to the elements nearby in the big rubble pile and across a wide space earmarked for housing that are going to be destroyed if no-one saves them. 

 

1 hour ago, TqB said:

I'm sure your "obsidian" is iron slag - visually identical but easy to tell the difference in the UK as obsidian is not an option (unless someone dropped it!).

 

I find loads around where I live in NE England, plenty of black but other colours are common too - here's a selection:

 

Well, what do you know, I often see lots and lots of that exact blue stuff in the same places.

 

You're 100% right TqB, it is iron slag! Thanks for the heads-up on that stuff; I never would've known any different if you hadn't mentioned it.

[abyssunder]

No obsidian there... melted glass from slag