Ordovician in Tennessee (Help!)

[Architeuthoceras]

Going out on a limb with this one.

Gonioceras ????

The only thing it resembles. Any more views to help substantiate?

 

[Terri]

I was actually googling gonioceras' earlier, here are a couple more views but I don't know if they will help. I've taken a dozen pictures of the thing and just can't get it right, I believe you can see the siphuncle but that pic. is way to blurry to post, I will try to get some better views tommorrow.

 

[Architeuthoceras]

I was actually googling gonioceras' earlier

Shooting for my job?

 

[Terri]

 

[Terri]

Hey Kevin, here is a picture of what looks like a siphuncle on the possible Gonioceras (blurry, sorry) and a shot of both sides.

 

[Terri]

Would the first one be a phragmacone and living chamber?

 

[Architeuthoceras]

To me, that end view pic confirms the Gonioceras ID.

All phragmocone, no part of the living chamber is visible. The septa and siphuncle only occur in the phragmocone. I don't see any of the outer shell on any of these latest fossils, do any of the others you found show the outer shell?

 

[Architeuthoceras]

Oops! Didn't see the photos.

That first one is a nice little breviconic cyrtocone, showing a constricted aperture so it is the phragmocone and living chamber, the outer shell seems to have mostly dissolved. A very nice little fossil

 

[Architeuthoceras]

The second pic is all phragmocone.

Some strange taphonomy going on in the first pic, it seems some of the internal mold has shifted inside the external mold, very interesting.

 

[Terri]

explanation??

 

[Architeuthoceras]

The gap between the last septum (the internal mold of the last chamber) and the living chamber (the internal mold of the living chamber) is very wide on top, like the living chamber (or phragmocone) has shifted. Or the last septum was very thick on the top side. The mold of the outer shell is very thick and on the left side seems to have left a notch in the mud. If the shell dissolved after the mud lithified, the internal molds of the chambers would be free to move around inside the mold of the outer shell. However, it looks like there is some lithified mud in between the body chamber and the phragmocone. It just looks like a lot happened to that fossil between the time it died and sank to the sea floor and the time the mud lithified (or maybe even sometime after that?).

 

[Terri]

Thanks Kevin, that is very interesting, I very much appreciate your taking the time to explain these things to me. I'm learning slowly but surely! I was just looking down into that gap with a flashlight and magnifying glass, I may be very, very wrong but I think I may see the siphuncle. I'll take another look at it tommorrow, maybe I can get a shot of it through the magnifying glass.

 

[Hajar]

Nice finds Terri. Do you ever see shalier, less cemented horizons allowing more of a view of external shapes?

 

[Terri]

Thanks Hajar, if I understand your question correctly, no I don't(except for this new location) The bedrock geology of the Central Tennessee Basin consists of Ordovician limestone, so I am surrounded by 14,580 sq. kilometers of limestone outcrops, and I haven't ventured outside of the basin into younger rocks...yet! But there is some shale, sandstone and bentonite scattereed about, mainly limestone though. But it's interesting you asked about shale,at the site where I found these last few fossils I have come across what I think is shale it's an almost blue/grey in color and breaks apart very easily and possibly some oil shale, I actually came straight home and googled shale, because it is so diifferent from what I'm used to seeing here.

 

[Terri]

Here are a couple of pics. of the possible Actinoceras posted a couple of days ago, I cleaned it up a little and took the pic. through a magnifying glass the second one shows some good detail when enlarged.