March 27, 2022 Peace River invertebrate unknown.

[Sacha]

Yesterday while looking for Miocene Echinoids I ran across the following piece which I almost tossed away, but the longer I looked at it, the more unusual it seemed. This section of the Peace is largely Miocene Peace River Formation and largely yields invertebrates with infrequent vertebrate fossils washed in. I tried to find a thread where @Coco and @Shellseeker discussed "Limestone algae" or something similar, but I can't exactly recall what it was. The piece in question was quite small and was found by Jack and Coco gave hime the ID. 

 

The piece I'm wondering about is quite large (relatively) and I wondered if it could be the same thing as Jack's. It definitely looks like more than a geologic oddity, but not really bryozoa ish or coral ish. 

 

Thanks for looking.

 

[caterpillar]

Oyster?

[Plax]

Looks like heavily burrowed bivalve shell as caterpillar suggests.

[Harry Pristis]

It does seem interesting, Sacha.  Please clean it up, air-abrade it if possible, and take close-up images.

[Coco]

Hi,

 

It doesn’t look like limestone algae, here are some examples

 

 

I think caterpillar and Plax are closer to the truth.

 

Coco

[Dave pom Allen]

maybe a type of stomatolite or oncolite

 

[Sacha]

1 hour ago, Harry Pristis said:

It does seem interesting, Sacha.  Please clean it up, air-abrade it if possible, and take close-up images.

 

I can try to pick some of the sand and gravel from the pores, but air abrasion is not an option. I get the impression that it is an encrusting organism though, from the impression you can see in the 2nd picture, although it isn't obvious. It looks like a thumb with a long nail stuck into play doe, or the impression of a long lost bivalve. I'll do what I can to try to present it better.

[Shellseeker]

10 hours ago, Sacha said:

I tried to find a thread where @Coco and @Shellseeker discussed "Limestone algae" or something similar, but I can't exactly recall what it was. The piece in question was quite small and was found by Jack and Coco gave hime the ID. 

Here is the thread, John

[Sacha]

17 hours ago, Harry Pristis said:

It does seem interesting, Sacha.  Please clean it up, air-abrade it if possible, and take close-up images.

 

I tried an ultrasonic cleaner to remove some of the trapped sand without much luck, but I think these relatively close and in focus pictures will help.

 

[Plax]

cliona bored thick oyster shell for me with the sponge borings resistant to dissolution.

[Sacha]

Confirmed by Roger Portell at the Univ of FL. I would not have believed it. Thank you everyone.

[Harry Pristis]

 

24 minutes ago, Sacha said:

Confirmed by Roger Portell at the Univ of FL. I would not have believed it. Thank you everyone.

WHAT was confirmed by Roger Portell??

[Sacha]

1 hour ago, Harry Pristis said:

 

WHAT was confirmed by Roger Portell??

 

That everyone except me was correct that this was a large bi-valve heavily eroded.......I'm still surprised because this is the biggest mollusk remains by far I've found in this layer by a factor of 10. Shells are very infrequent and no bigger that 2 inches or so for the most part.

[Harry Pristis]

Thanks.  I can't remember finding any large mollusks in the Peace River sediments.  Mollusks I did encounter were usually silicified.  But, maybe I didn't look in the right places.

[Sacha]

1 hour ago, Harry Pristis said:

Thanks.  I can't remember finding any large mollusks in the Peace River sediments.  Mollusks I did encounter were usually silicified.  But, maybe I didn't look in the right places.

 

That's why I have a hard time with this. Small silicified scallops, high spired gastropods and oysters not bigger than 2 inches and steinkorns of clams and small gastropods is all I've found in 2 years of pretty intensive digging in this section of river. Mollusks of any kind are not common. This thing is orders of magnitude different. 

[Plax]

Oysters have calcitic shells which are more resistant to dissolution. Yours is partially dissolved away though, with the cliona borings standing out in relief because they were sediment filled and indurated before more of the shell dissolved. We see this here in North Carolina but it's not common. I have some Cucculea "shells" represented by their cliona borings where you can see the steinkern through the gaps from the new Egypt Fm of NJ. It was great that you posted this fossil as it illustrates many interesting things that happened to the shell post mortem and during diagenesis.

[Sacha]

2 hours ago, Plax said:

Oysters have calcitic shells which are more resistant to dissolution. Yours is partially dissolved away though, with the cliona borings standing out in relief because they were sediment filled and indurated before more of the shell dissolved. We see this here in North Carolina but it's not common. I have some Cucculea "shells" represented by their cliona borings where you can see the steinkern through the gaps from the new Egypt Fm of NJ. It was great that you posted this fossil as it illustrates many interesting things that happened to the shell post mortem and during diagenesis.

 

Thanks for the detailed explanation. I appreciate you taking the time to help me get it through my head.