Devonian Coral - B.C. Rockies

[Wrangellian]

I picked up a few pieces of this stuff at a Devonian site in the Bull River Valley this past August. The tour guides weren't much help, and it's hard to find info about corals if you don't know the terminology very well and maybe there isn't much literature on corals from this site? If I could get the possibilities narrowed down, that would be better than nothing. I just figured it looked distinctive enough that someone might recognize it. Very small corallites, 1mm scale or less. All I know about the site is that it is supposed to be Devonian.

 

Forgot scale on this first piece but the following ones have it.

There is at least one other type (maybe two) on this piece as well, toward the right.

[Wrangellian]

[Wrangellian]

I believe we're looking at the bottom of the colony here, the top in the 2nd pic, edge in 3rd pic:

 

[Wrangellian]

3 more coral pieces. It looks like 2 different corallite sizes here - not sure if that means 2 different taxa?

Sorry, forgot the scale cube again. The middle piece is about 55mm long, and the corallites are at least 1mm, or a little bigger.

[FranzBernhard]

Eric, I didn´t know that you visited the Devonian north of me .

I may have picked up totally similar specimens in the Plabutsch-Formation.

 

These are very nice tabulate coral colonies, probably favositids, maybe genus Favosites?

Can you see tabulae? But often, they are not preserved, though.

 

2 hours ago, Wrangellian said:

not sure if that means 2 different taxa?

Yes. Corallite size is an important distinguishing criterion.

 

Considering species of the genus Favosites, I have read, that most of the 400 species and subspecies were described only once.

 

Considering the small size of corallites, there is a species in the Plabutsch formation (F. alpinus), that has corallite diameters of only 0.5-0.7 mm.

 

@TqB, @minnbuckeye

 

Greetings!
Franz Bernhard

[TqB]

This one (from photo 5) looks like Alveolites - "calices oblique, crescentic or irregularly angular" (Treatise).

 

[Wrangellian]

Thanks both... To be I suppose I'll have to do as recommended: cut and polish a slice. At the moment I don't have the means. Anyway I quite like them au naturel, but if necessary to get a reliable ID, I will take a slice when I can.

[Wrangellian]

18 hours ago, TqB said:

This one (from photo 5) looks like Alveolites - "calices oblique, crescentic or irregularly angular" (Treatise).

 

I would have thought this was an artifact of the way the rock cleaved at an angle thru the corallites..? 

Other pieces were cleaved more parallel or perpendicular to them.

[Wrangellian]

19 hours ago, FranzBernhard said:

Eric, I didn´t know that you visited the Devonian north of me .

I may have picked up totally similar specimens in the Plabutsch-Formation.

 

These are very nice tabulate coral colonies, probably favositids, maybe genus Favosites?

Can you see tabulae? But often, they are not preserved, though.

 

Yes. Corallite size is an important distinguishing criterion.

 

Considering species of the genus Favosites, I have read, that most of the 400 species and subspecies were described only once.

 

Considering the small size of corallites, there is a species in the Plabutsch formation (F. alpinus), that has corallite diameters of only 0.5-0.7 mm.

 

@TqB, @minnbuckeye

 

Greetings!
Franz Bernhard

Thanks Franz, I was not sure that some Favosites were that small. It looks like tabulae where the rock cleaved parallel to the corallite growth, as in pics 3 and 8, maybe just barely visible in those pics.

[TqB]

6 hours ago, Wrangellian said:

I would have thought this was an artifact of the way the rock cleaved at an angle thru the corallites..? 

Other pieces were cleaved more parallel or perpendicular to them.

Could be, though I think I can see some shapes that don't look like oblique simple polygons. As always, properly oriented polished sections should clear it up.

[Wrangellian]

Here is the full-size version of that pic, if it helps any... though I suppose it's going to be as you say: polished sections needed.

 

[Wrangellian]

...and the full-size version of the adjacent part of that piece:

 

[TqB]

Hard to be sure - for example, this patch looks like Alveolites:

 

Here's a Silurian one of mine (Wenlock, UK), top surface of colony - compare the central area where the corallites are less crescentic:

(scale in mm)

 

 

 

[Wrangellian]

Hmmm.. could be. What does that one look like along the side (edge)?

[TqB]

6 hours ago, Wrangellian said:

Hmmm.. could be. What does that one look like along the side (edge)?

You can only really see anything on the broken edge, which gives pretty much a longitudinal section - typical favositid.

 

 

 

And here's a random section in a piece of Devonian "marble", from Devon, UK.

[Wrangellian]

Well that side section looks a lot like mine, to my untrained eyes... maybe the random section too but maybe my pieces aren't so well preserved so it's hard to tell. 

So Alveolites is a favositid?

[TqB]

10 hours ago, Wrangellian said:

So Alveolites is a favositid?

Yes - Order Favositida, suborder Alveolitina, according to the Treatise (which is getting on a bit - 1981 - but generally reliable still).

[Wrangellian]

Here's another one of those branching corals.. I'm curious what these might be, too:

 

[TqB]

4 hours ago, Wrangellian said:

Here's another one of those branching corals.. I'm curious what these might be, too:

Thamnopora is a good bet, it's cosmopolitan in the Devonian though I'm sure there are other possibilities.

[Wrangellian]

Thanks again. I'll go with these IDs.

[Wrangellian]

One more thing I picked up at that site, that I'm not sure what it is. Seems more like a ball than a disk. Is it just a concretion, or something biological? Hard to photograph, partly because it's sort of featureless, partly because I'm photoing a bulky object indoors...

 

Pic 3 is a side view below the edge you see in pic 2.

 

[Shamalama]

Maybe a massive Bryozoan colony? The second pic seems to have vertical features that remind me of Bryozoan.

[Wrangellian]

Thanks Dave.. I wonder about that, but wouldn't I see pores or some other features along the side or the flat top? Maybe the striations are just crystalline or slickenside in nature?

Do you get big round concretions like this in limestone? I know they occur in shale...

[Shamalama]

I've seen very fine vertical features like those before but never with a flat surface, so maybe I am wrong. So the surface is completely smooth and has no features even under magnification? Does it look as though it was worn smooth like by a glacier or water?

[Wrangellian]

Those striations are on a flat broken surface, and I'm thinking it is a vein of some sort that cut thru the 'ball' and it was subsequent split along there. The flat upper surface has been exposed/weathered to some degree, and looking closely I think I see faint pores of some sort on that flat surface, but trying to take a pic would be difficult. I could try.

I can't tell whether the flat top was broken (in which case it might be a concretion?), or if we're looking at the flat top of a hemispherical organism/colony.