Possible Jurasic Mollusca Bivalve Buchia

[Ema Tzedakah]

Hello. This is my next mystery. It's been looked at in the precleaned state and dismissed as a cool rock. I beg, to differ and need your thoughts. My reasons for thinking this is a fossil/ fossil impression are as follows: 

 

1) As I cleaned, the left edge (see ladt pick with knife), began to show evidence this is on top of the matrix, not part of it. Likely matrix of shale-chert so please, take that into consideration. Extremely odd charts in my area 

 

2) Looking at the picture with my finger, examine that small white portion. That appears totally different from the rest. 

 

3) I do see a horizontal pattern matching the only other buchia so. I could find online. I've included that picture as well - All copyright remains with the Dr. Richard Paselt per the tag seen in the photo. 

 

Thank you for your time. If this is buchia, then it's a glacial find and came to the East Tennessee, Douglas Lake area of the French Broad river, Dandridge Docks, Dandridge, TN by water. That's where I found it. This is supposedly Mid-Ordovician in this area. Tennessee is an extraordinary place and it's  State Fossil is a Jurrasic period one. 

[Plantguy]

Interesting find Ema.  

I can see a resemblance to a Buchiid clam but I dont see any concentric ribbing (I see fracture lines and pitting from weathering) and while the shape is somewhat similar I'm not sold on that as  a fossil. Looks like it almost has a rounded edged/flat base which isnt consistent with any of the Buchiid finds I have. Once in a while you'd find both valves of the clam still articulated but the individual ones dont have that kind of rounded base. I'm thinking it non-fossil and looks more like what you already described initially--- a cherty nodule in limestone...

 

Hoping someone more familiar with your area or one of the others sees something different. As reference here's one good and a really bad picture of a number of different Buchia species and their different shapes/forms/modes of preservation that I collected from California years ago. 

Continued hunting success! Thanks for showing us! 

Regards, Chris 

 

 

 

[Fossildude19]

Ema, 

 

According to this geologic map: 

 

 

There are no Jurassic aged exposures in Tennessee. 

A glacial erratic would be a slim possibility. 

 

Your item could be a concretion/chert nodule, (which I am leaning towards)  or some other inclusion, or, ... it actually could be an internal mold of some other bivalve. 

I think calling it a Buchia sp. would be hedging all bets, in my opinion, and is probably incorrect.   

 

Sometimes ID's can't be made from photos, so you may want to take this to a museum or university paleontologist, and have it looked at in person. 

 

 

 

 

[FossilDAWG]

Hi Ema,

 

I don't actually see anything to confirm that your specimen is definitely a bivalve fossil, much less a Buchia.  I see a weathered chert nodule.  Although the shape is bivalve-like, there is no uneroded surface that shows any bivalve features.  The ribbing you mention is a typical fracture pattern for chert nodules.

 

There is no marine Jurassic anywhere in Tennessee.  The state fossil you mention, Pterotrigonia thoracica, is common in the Late Cretaceous Coon Creek Formation.

 

There are a lot of great fossils to be found in Tennessee, so keep on looking! 

 

Don

[jpc]

I agree with FossilDAWG

[Ema Tzedakah]

You ALL are so kind!! After I posted this, something took me towards brachiopod, not bivalve, internal impression. That better explains its curved nature horizontally. And the not quite concentric horizontal lines it see. 

 

The area I'm in is consistent with funding mass die off "slabs" of Ordovician age brachs!! I'll return to the area because I believe I saw a few of the sedimentary bedding slabs; I didn't look closely thinking they were just more unusual things chert can do!! 

 

We can consider this closed... I'll bring back a slab if it looks good. 

 

Hey - I'm 60, a professional rock hound 10 years. But now, I'm living my final bucket list dream. And I can't begin to express how wonderful it is to me, you answer, but never beat me down! You recognize, I've got some good info, but you always acknowledge gently what I'm seeing and why it does not match! 

 

Thank you!!!

 

Oh god...the typos!! Try to read beyond. Bad day to type.

[Ema Tzedakah]

5 hours ago, Fossildude19 said:

Ema, 

 

According to this geologic map: 

 

 

There are no Jurassic aged exposures in Tennessee. 

A glacial erratic would be a slim possibility. 

 

Your item could be a concretion/chert nodule, (which I am leaning towards)  or some other inclusion, or, ... it actually could be an internal mold of some other bivalve. 

I think calling it a Buchia sp. would be hedging all bets, in my opinion, and is probably incorrect.   

 

Sometimes ID's can't be made from photos, so you may want to take this to a museum or university paleontologist, and have it looked at in person. 

 

 

 

 

Though I'm satisfied I did not find a Jurrasic bivalve, I did read (I thought), there is a Jurrasic period area in/about Coon County in TN? I'll choose to defeat to you all here though. And there's a University I will take my specimen to, as well as likely gift the Rugose fossil coral I found at same location. Thanks!!!

[FossilDAWG]

There actually isn't a Coon County in Tennessee.  That's not surprising if you think about the history of the state and the old slang meaning of "coon".  There is a Coon Creek, in McNairy County, which is the best-known and most fossiliferous outcrop of the Coon Creek Formation.  The outcrop is famous (amongst paleontologists anyway) for its incredibly diverse and well preserved marine fossils.  However they are Upper Cretaceous, not Jurassic.  BTW the exposure is now controlled by the Pink Palace Museum and you have to have permission to collect there, which usually means belonging to a club.  You might have seen something online where the site is called Jurassic, there are tons of mistakes like that online and after Jurassic Park everything "dinosaur age" gets called Jurassic.  There is no marine Jurassic anywhere east of the Mississippi, so Jurassic marine fossils don't occur in Tennessee or anywhere north where glaciers might have picked up a fossil-bearing rock and moved it.  That's unfortunate, I wish there was some Jurassic to collect in the east.  There are some Jurassic lake deposits with rare fish and plants, not in Tennessee but in further east Virginia and Connecticut, but you will not find Buchia or ammonites or ichthyosaurs there.

 

Don

[Ema Tzedakah]

Thanks Don and yes, I meant Coon Creek. I've probably misread something is all.

 

Karen, aka Ema

[Ema Tzedakah]

On 5/27/2021 at 10:40 AM, Fossildude19 said:

Ema, 

 

According to this geologic map: 

 

 

There are no Jurassic aged exposures in Tennessee. 

A glacial erratic would be a slim possibility. 

 

Your item could be a concretion/chert nodule, (which I am leaning towards)  or some other inclusion, or, ... it actually could be an internal mold of some other bivalve. 

I think calling it a Buchia sp. would be hedging all bets, in my opinion, and is probably incorrect.   

 

Sometimes ID's can't be made from photos, so you may want to take this to a museum or university paleontologist, and have it looked at in person. 

 

 

 

 

I am still learning the lingo and latest realized, internal cast/ mold is what I thought this was. Thinking, it looks all cherty because of how strange things can be in the Lenoir Formation. 

 

So I knew the location is Mid Ordovician and, had this been an internal cast, just felt like, how'd this get here? 

 

Thanks!