Kaloot: Separating fossil from modern shells

[Max-fossils]

Hi all,

 

Today at a flea market I purchased a small handful of shells found on the Kaloot (NL), where you can find fossil sharkteeth as well as fossil seashells (and other fossils). He assured me that at least some (if not all) are fossils, which is true: the Pliothyrina in the middle is extinct, so it has to be a fossil; and many of the astartes on the bottom seem to be fossilized too. But I'm not sure that all the shells are fossilized. Therefore I was wondering, does anyone know how to separate fossil shells from modern ones?

 

Best regards,

 

Max

[doushantuo]

yes, I might help you.

Hang on a minute

Colour changes*,chipping and other signs of predation and/or being tumbled about in the swash zone, holes,breakage,valve separation . endolith infestation,periostracum loss,epizoan encrustation,prolly a host more.

Epizoans are the beasties or algae that like to live on or on the inside of a shell.

Bivalves can live in the sediment(at various depths),or on it.This will affect how they might look as fossil.

The shells can undergo mineralogical changes during burial,sometimes even when they are still alive.

If a shell is composed of aragonite,it is easier to dissolve than when it is made up of calcite.

And the water temperature affects its capacity to dissolve shells as well.

* loss of colour in about two years in tropical waters

 

ctidal-regime-of-north-sea-tidal-flats.pdf

 

outtake:

 

[doushantuo]

outtake two

[doushantuo]

from ESR:

 

zusc_al._2003.pdf

[doushantuo]

miscellaneous forms of shell preservation:

[doushantuo]

from the North Sea area:

all are Mya Arenaria,in A :dead specimens ,but still with both valves attached to each other.Area:German Wadden Sea(I think)

 

[Max-fossils]

1 hour ago, doushantuo said:

yes, I might help you.

Hang on a minute

Colouration changes,chipping and other signs of predation and/or being tumbled about in the swash zone, holes,breakage,valve separation . endolith infestation,periostracum loss,epizoan encrustation,prolly a host more.

Epizoans are the beasties or algae that like to live on or on the inside of a shell.

 

Alright, thanks for the help!

But how do I do this if I don't always know the exact species? Also, some of the things you mentioned above are also present on modern shells. With the coloration changes, how can I know if it changed when I don't know the original color? Chipping often occurs with modern shells too. I also have many modern shells with signs of predation on them. Holes and breakings are also common in modern shells (don't have an example because I don't bother to pick up broken shells ). About 95% of the bivalves I find are separated from their other valve. With the epizoans, again I think that you can also have modern shells with them. 

What's a "swash zone"? I also don't know what "endolith infestation", and I don't know how to recognize periostractum loss...

 

Knowing you usually make very true and helpful comments, I have the feeling I understood something wrong... So can you please help me?

[doushantuo]

endolith:any creature that is able to bore into stone.

Max,for recognition of which kind of shell you're looking at,there are guides for the layman.

There also genus and species descriptions in the zoological and paleontological literature.

If they are of high quality,they will show all of the features that make up the genus /species. 

[doushantuo]

a page from a monograph:

[doushantuo]

black & white:

wesselmytiluhollandcainozdownload.pdf

[doushantuo]

a PPT presentation:

mollusc-shell.pdf

[DPS Ammonite]

The swash zone is where the ocean waves wash over the beach.

 

The periostractum is the tan/brown/black protein skin that covers shells as shown is the picture of the razor clams. The periostractum is rarely preserved in fossils.

 

You probably cannot tell whether or not your shells are fossils if the species still lives in the area unless you can date the shell or a rock layer containing the shell. The extinct shell may be a fossil if the shell became extinct more than 10,000 years ago. Just because a shell is a fossil, more than 10,000 years old, doesn't mean that it is has changed much since it died and has become "fossilized".  A 300 year old shell may not look any different from a 10,000 or 1,000,000 year old shell.

 

 

[doushantuo]

ben ook beetje schelpengek

Periostracum:

clarkbiominbivalvcalcific16-3-617.pdf

[doushantuo]

endoliths & periostracum:

 

muss-periostrac-deep-sea-redo-com-microbial-habitat-57f2d35200cdf.pdf

[doushantuo]

BS & DS on sclerochronology

Extremely good piece,but that kinda figures

[Max-fossils]

3 hours ago, doushantuo said:

BS & DS on sclerochronology

Extremely good piece,but that kinda figures

Alright, thanks for all the files! I'll have a good look at them once I'm home and have my computer; my phone doesn't seem to like pdf s a lot. 

[Max-fossils]

3 hours ago, DPS Ammonite said:

The swash zone is where the ocean waves wash over the beach.

 

The periostractum is the tan/brown/black protein skin that covers shells as shown is the picture of the razor clams. The periostractum is rarely preserved in fossils.

 

You probably cannot tell whether or not your shells are fossils if the species still lives in the area unless you can date the shell or a rock layer containing the shell. The extinct shell may be a fossil if the shell became extinct more than 10,000 years ago. Just because a shell is a fossil, more than 10,000 years old, doesn't mean that it is has changed much since it died and has become "fossilized".  A 300 year old shell may not look any different from a 10,000 or 1,000,000 year old shell.

 

 

Alright, thanks so much! Even though this is kinda bad news, it's not too bad because at least I know what to expect. I'll try to ID each of the shells using the guides I have, and then find out whether it could be a possible fossil or not.

[Innocentx]

Just for the heck of it, periostracum preserved in chert, Early Permian.

[doushantuo]

Thanks for that ,Inn