unknown coral obtained at a rockhound event

[Wrangellian]

I saw this chunk on a sales table at the recent Rendezvous of BC rockhound clubs here on the Island. Had to have it, though I keep telling myself to avoid fossils with no provenance.

Anyone recognize it or have any hunches as to ID and especially location of origin? I guess somewhere on the eastern half of the continent...

It appears to be a mix of cherty and crystallized composition. Whoever owned it before didn't treat it very kindly (lapidary types)... Apparently there once was a label of some sort glued to the top, and the rough saw cut which I hope to flatten better and polish someday.

 

 

[Lone Hunter]

 

Maybe something like Lithostrotionella?  

[Wrangellian]

Thx, that might help narrow the possibilities for strat/location down slightly if others concur.

[TqB]

It looks like Arachnophyllum, which is Silurian. The vertical section is distinctive.
(Be aware that the majority of Google images are wildly misidentified trade specimens from Morocco and no help at all!)

Forum example:
http://www.thefossilforum.com/index.php?/topic/35810-michigan-fossil/

Textbook example:

Edited June 21, 2022 by TqB

[Wrangellian]

22 hours ago, TqB said:

It looks like Arachnophyllum, which is Silurian. The vertical section is distinctivel.
(Be aware that the majority of Google images are wildly misidentified trade specimens from Morocco and no help at all!)

Forum example:
http://www.thefossilforum.com/index.php?/topic/35810-michigan-fossil/

Textbook example:

OK, thanks Tarq. Does that mean mine could be from anywhere, including Morocco, or is it most likely from Michigan or somewhere thereabouts?

[TqB]

1 hour ago, Wrangellian said:

OK, thanks Tarq. Does that mean mine could be from anywhere, including Morocco, or is it most likely from Michigan or somewhere thereabouts?

It's widely distributed in N. America and Europe - I haven't seen it from Morocco!

Specimens like yours (often silicified) crop up commonly in Great Lakes social media fossil groups, including from Michigan. The Treatise (1981) lists occurrences from Kentucky, Indiana, Michigan, Iowa, Tennessee and I've seen people post it from Wisconsin.  

Edited June 21, 2022 by TqB

[Wrangellian]

1 hour ago, TqB said:

It's widely distributed in N. America and Europe - I haven't seen it from Morocco!

Specimens like yours (often silicified) crop up commonly in Great Lakes social media fossil groups, including from Michigan. The Treatise (1981) lists occurrences from Kentucky, Indiana, Michigan, Iowa, Tennessee and I've seen people post it from Wisconsin.  

Is there nothing about the look (preservation) of this chunk that is characteristic of any specific place - do they commonly look like this all over that area? I'm hoping that someone will recognize it by looking (and maybe by knowing the relative abundance from each place and how commonly material from those places is found in the fossil or lapidary market), rather than just by the occurrences of the taxon listed in a book.  If "probably from Michigan" is the best I can do for location info then that will be better than nothing. I've got a lot of labels with question marks on them...

[TqB]

@LisaL may be able to narrow down the area.

[LisaL]

Thank you for the tag, @TqB! My understanding is that Arachnophyllum in the Great Lakes region originates from the Niagara Escarpment rocks that arch from eastern Wisconsin over the eastern Michigan UP and down into Ontario and northeastern NY. I think the Cordell Dolomite of the Manistique Group is where most of the Arachnophyllum in our Facebook groups from eastern Wisconsin and northern Michigan come from, based on the old papers I’ve referenced while trying to source mine. The Cordell Dolomite has silicified fossils, so it seems like a good possibility? 
 

Here’s a post about an Arachnophyllum from the Burnt Bluff group, another middle Silurian section right beneath the Manistique Group on the stratigraphy chart.  http://viewsofthemahantango.blogspot.com/2014/08/arachnophyllum-sp-coral-from-michigan.html?m=1
 

Im not sure whether it occurs much outside the middle Silurian. 
 

here are a couple of links to sources that might be helpful. 
 

“The Silurian Rocks of Michigan and their Correlations”
https://deepblue.lib.umich.edu/bitstream/handle/2027.42/48577/ID435.pdf;sequence=2#:~:text=The%20Silurian%20rocks%20that%20are,554%2D556).
 

Sections of the Niagara strata that may have Arachnophyllum:

Edited June 21, 2022 by LisaL

[LisaL]

Expanding east a bit more, the Fossil Hill Formation of southern Ontario also looks like a possible provenance for your specimen:

 

 

 

Here's a FF thread from 2015 with an Arachnophyllum from the Fossil Hill Fm:

 

http://www.thefossilforum.com/index.php?/topic/56291-silurian-spongerugose/

 

@FossilDAWG would be a good person to ask! I think he's done a lot of work in these formations.

 

 

 

 

Edited June 21, 2022 by LisaL

[Wrangellian]

Thanks Lisa, I see the stratigraphy and the outcrop map, I think we're closing in on the location, but I don't think we can get any further until someone comes along and recognizes the material and says "oh yes, that looks like like these samples collected from the shores of Lake X" or "the Y Quarry"... but that rarely seems to happen.   Will wait for Don to chime in.

It looks like a lot of those formations are dolomite, so we may never be able to narrow it down very far, but at least we tried. Is the Fossil Hill Fm dolomite also? I guess it's more likely to be from a Canadian location given that I am in Canada, but not necessarily. Rock seems to travel around a lot and I've got a lot of rocks (and some fossils such as pet wood) from the Western U.S.