Jump to content
Chelydra

fossil quahog

Recommended Posts

Chelydra

This amazing bivalve fossil was a gift. The giver had no info to offer. I am curious about what its origins might be - where/when; about how old it might have been when it died (it is 6 inches across and has several hundred growth ridges); and I would like to understand how fossilization can result in what appears to be a set of perfectly intact valves, complete with so much detail - in other words, the shells are much heavier than living shells would be, what has replaced the calcium bicarbonate to make the shells so much heavier?

53745081_10155908063515974_2014753374548787200_n.jpg

53745113_10155908063455974_1770575052023005184_n.jpg

quahog_interior.jpg

Share this post


Link to post
Share on other sites
FranzBernhard
47 minutes ago, Chelydra said:

when

According to fossilworks.org, Quahogs (Mercanaria mercenaria) are known since 16 million years. But I don´t know, which specific formations along the North American east coast contain them.

 

49 minutes ago, Chelydra said:

where

From Florida to Canada, according to wikipedia:

https://en.wikipedia.org/wiki/Hard_clam

 

50 minutes ago, Chelydra said:

about how old it might have been when it died

Don´t know how long they can live. Its an intertidal species, they could possibly grow rather fast (oysters do this, for example).

Interestingly, there is a detailed discussion about the age of the other Quahog, the Oceanic Quahog (Arctica islandica). Thea can reach an age of nearly 400 years:

https://en.wikipedia.org/wiki/Arctica_islandica

But this is a subtidal species, usually less harsh and more stable conditions than the interdital.

 

51 minutes ago, Chelydra said:

the shells are much heavier than living shells would be, what has replaced the calcium bicarbonate to make the shells so much heavier?

Does it really have a golden shine to it (it appears so on the pic)? Than it is (partially) replaced by pyrite (FeS2) about twice as dense as calcium carbonate.

 

@Max-fossils, @MikeR

 

Btw, very nice shell, thanks for sharing, and welcome to TFF!
Franz Bernhard

Share this post


Link to post
Share on other sites
minnbuckeye

Nice specimen!! I am just a casual collector and have found some Mercanaria in the York formation of Virginia and the Tamiami formation of Florida. So pinpointing a location is probably unlikely unless MikeR can differentiate differences .     

 

 Mike

Share this post


Link to post
Share on other sites
Max-fossils

Fantastic specimen! Gorgeous!

It definitely does appear to be a Mercenaria mercenaria, or at least a related species. I can't tell if the golden/brown color is indeed pyrite, or just a coloration due to how it sat in the matrix (perhaps with just the hinge coming out of the matrix or the other way around), or because it's wet. Then again, you don't see pyrite shells this young too often, so right now I think the best reason for the two different colors is that one part was exposed to air while the other sat in matrix (this would also explain why the insides don't have different colors). 

 

This species had, and still has, a rather wide distribution, so accurately guessing the location (and hence the precise age and formation) is gonna be tough...

 

Welcome to TFF!

 

Max

Share this post


Link to post
Share on other sites
Al Dente

I doubt if much if any mineral replacement has occurred with this particular fossil. I find modern Mercinaria on the beach and they can be very heavy for their size.

Share this post


Link to post
Share on other sites
Chelydra

Wow. This is rather awesome - thanks so much for the info. Yes, I think the lighter hinge was exposed - the reddish/brown has no shine of pyrite. In my area of Lakefield, Ontario, Canada, we are known for Isotelus.

 

As to whether this shell is a fossil at all, I wondered that. But I have a modern quahog shell that is much lighter...Cheers

20190310_121118.jpg

20190310_121153.jpg

Share this post


Link to post
Share on other sites
Max-fossils

That's a very nice trilobite!

Share this post


Link to post
Share on other sites
Rockwood

It's frightened so it rolled up in a ball. :)

Share this post


Link to post
Share on other sites
MikeR

I agree with what everyone else says.  It is either the Northern Quahog Mercenaria mercenaria or the Southern Quahog Mercenaria campechiensis.  I would say the latter as M. campechiensis is more rounded on the posterior portion of the shell.  Mercenaria date back at least to the Miocene in deposits from Virginia to Florida and I have found very large excellently preserved M. campechiensis throughout the Pleistocene LINK.  Without knowing any details however, it will be impossible to say if it is a fossil or not.

 

Mike

Share this post


Link to post
Share on other sites
FossilDAWG
On 3/10/2019 at 12:40 PM, Chelydra said:

Wow. This is rather awesome - thanks so much for the info. Yes, I think the lighter hinge was exposed - the reddish/brown has no shine of pyrite. In my area of Lakefield, Ontario, Canada, we are known for Isotelus.

 

As to whether this shell is a fossil at all, I wondered that. But I have a modern quahog shell that is much lighter...Cheers

20190310_121118.jpg

20190310_121153.jpg

Nice Isotelus!  I still have quite a few trilobites and other fossils I collected at the Lakefield Quarry back in the late 1970s/early 1980s.  However I have heard that the current property owner won't let anyone collect, not even researchers from the Royal Ontario Museum.  I drive past there sometimes when I go back to Ontario to visit family, and I sure wish I could stop in for a bit but it isn't worth getting arrested or worse.

 

Don

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Recently Browsing   0 members

    No registered users viewing this page.

×