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List of Ways Fossils are Preserved


BobWill

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11 hours ago, Harry Pristis said:

3    External Cast   (original outer surface dissolves and space fills with solidifying material)

 

4    Internal Cast    (original inner surface dissolves and space fills with solidifying material)

 

I'm not sure how I missed this thread, but I'd like to point out that there is no real difference between 3 & 4 in the common case of bivalves:  In either case, the result is an external cast.  "Surface" is a weak descriptor for containment wall, partition, or barrier.  But, the simplest way to correct the problem is to invert the sequence in "4  Internal Cast" to something like:

 

"(space fills with solidifying material and then the original containment wall dissolves)"

 

Just trying to help.

Great idea, thanks for the help. Maybe even "original shell" for even more clarity.

 

Wouldn't the difference between 3 & 4 in the case of one valve of a bivalve be that 3 is convex and 4 is concave, since a cast is a copy of the original?

 

Any thoughts on adding resin, and do you know a better term to use?

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20 minutes ago, BobWill said:

Great idea, thanks for the help. Maybe even "original shell" for even more clarity.

 

Wouldn't the difference between 3 & 4 in the case of one valve of a bivalve be that 3 is convex and 4 is concave, since a cast is a copy of the original?

 

Any thoughts on adding resin, and do you know a better term to use?

Stay away from the terms concave and convex when determining whether a shell surface is internal or external. There are many examples of shells (especially brachiopods) with exteriors that are concave. Also, the interior of the top smaller valve of an Exogyra ponderosa is convex.

 

Here is how I would define external/ internal cast: a replica of the exterior/ interior surface, not a mirror image, of the original shell or skeleton. 
 

Sometimes you see both sides of a cast as in the case of an opalized bivalve from Australia.

 

My goal is to leave no stone or fossil unturned.   

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9 hours ago, DPS Ammonite said:

Stay away from the terms concave and convex when determining whether a shell surface is internal or external. There are many examples of shells (especially brachiopods) with exteriors that are concave. Also, the interior of the top smaller valve of an Exogyra ponderosa is convex.

 

Here is how I would define external/ internal cast: a replica of the exterior/ interior surface, not a mirror image, of the original shell or skeleton. 
 

Sometimes you see both sides of a cast as in the case of an opalized bivalve from Australia.

 

That's a good point that I ignored in my over-generalization. Maybe I should have said "typical clam" instead of bivalve but I was trying to make it easier to visualize. Taking that into account, would you agree with my decision to make a distinction between items 3 & 4 that Harry wanted to combine? I also like replica as another term for copy, though the difference is minimal. I will probably omit "not a mirror image" since one of the criteria for my definitions was to make them fit on a single line for uniformity and to fit the whole list on one page.  I was not totally happy with all of the compromises that forced so I'm still trying to be flexable.

 

I haven't seen the bivalves from Australia but I assume they are of open or separate valves if you can see both inside and outside surfaces. Unless there is a term for that form I will probably stay with the more commonly found versions for the list.

 

What is your opinion on resin as a fossil?

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Okay here is the latest list. I am very surprised it has grown so much since the beginning of the thread, from 20 to 30. Thanks to everyone for all the help.

 

               30  WAYS  FOSSILS  CAN  BE  FORMED

 

                                          DUPLICATION

 

1    Internal Mold  (minerals in contact with inner surface solidify then original dissolves)

 

2    External Mold  (sediment in contact with outer surface solidifies then original dissolves)

 

3    External Cast   (original outer surface dissolves and space fills with solidifying material)

 

4    Internal Cast    (original inner surface dissolves and space fills with solidifying material)

 

                                       MINERALIZATION

 

5    Permineralization    (space between cells fills with minerals that solidify)

 

6    Petrification    (space between cells fills with silica binding to cellulose)

 

7    Replacement    (cells replaced with new minerals that solidify)

 

8    Recrystallization    (replacement when the new minerals are a crystal form)

 

                                            DESICCATION

 

9     Remains preserved in a Peat Pit

 

10   Remains preserved in a Tar Pit

 

11   Remains preserved in Frozen Tundra

 

12   Remains preserved by Mummification

 

                                             ICHNOFOSSILS OR TRACE FOSSILS

 

13   Tracks

 

14    Infilled burrows

 

15    Coprolotes or droppings

 

16    Feeding traces

 

17    Urolites or urine splatters

 

18    Regurgitants or vomit

 

19    Body rests

 

20    Gastroliths

 

21    Bite marks

 

22    Bio-sedimentological structures like stromatolites

 

23    Termite mounds

 

24    Hardened plant resin

 

                                               OTHERS

 

25   Carbonization    (thin carbon film formed by chemical change)

 

26   Coalification    (carbonization occurring by much slower processes)

 

27   Adpression      (compression-impression)

 

28   Resin Inclusion   (Life trapped in resin which hardens into amber or copal)

 

29   Bioimmuration   (impression formed on a shell by growing over another life form)

 

30   Condensed Phosphorite Pseudo-Steinkerns  (bioimmuration replica cast in phosphorite)

 

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1 hour ago, BobWill said:

Okay here is the latest list. I am very surprised it has grown so much since the beginning of the thread, from 20 to 30. Thanks to everyone for all the help.

 

               30  WAYS  FOSSILS  CAN  BE  FORMED

Give a good definition for cast and mold and point out subtypes, interior and exterior, when only partially preserved. Good diagrams would be helpful.


 

Add

 

1 Cast with all surfaces preserved.

 

2 Mold with all surfaces preserved.

 

3 Borings such as those made by sponges and acorn barnacles.

 

4 Virtually unchanged (original material) but over 10k years old; this happens with wood, bone and shells.

 

5 Chemical traces of life such sterols, dna, unusual isotope ratios, etc.
 

 

1 hour ago, BobWill said:

30   Condensed Phosphorite Pseudo-Steinkerns  (bioimmuration replica cast in phosphorite)

 

I would get rid of the last one; can you explain it? I think that it is a combination of the types that you already mentioned.

 

 

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See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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2 hours ago, DPS Ammonite said:

Give a good definition for cast and mold and point out subtypes, interior and exterior, when only partially preserved. Good diagrams would be helpful.


 

Add

 

1 Cast with all surfaces preserved.

 

2 Mold with all surfaces preserved.

 

3 Borings such as those made by sponges and acorn barnacles.

 

4 Virtually unchanged (original material) but over 10k years old; this happens with wood, bone and shells.

 

5 Chemical traces of life such sterols, dna, unusual isotope ratios, etc.
 

 

I would get rid of the last one; can you explain it? I think that it is a combination of the types that you already mentioned.

 

 

 

 

Ha ha! You're making my effort to keep it all on one page very difficult John ;)

I'm okay with a cast having interior and exterior as one fossil but since a mold with both would have them in separate pieces I'm going to let folks think of them as two fossils to keep it simple and less cluttered up with things that would need too much explanation to fit on a single page well. If there are scientific terms you might see in a paper for those that could be Googled I might use them. That approach might eliminate the last item too. It is explained in the comment above from doushanto but it may be a little hard to search for compared to the others and pretty rare. On the other hand if it gets people wondering enough to inquire that would be a good thing.


I will add "and borings" to bite marks because of the similarity of intent.

 

So, is it still "fossilization" if there is no change? I've never given that any thought before.

 

As for chemical traces I do remember reading something about that so I need to decide how best to include it in a way that the average person might actually use it. I only know about the dating technique using isotope ratios. Are they something looked at in ways that include actual remains or traces of life? I would have to include oxygen that creatures exhaled if I go in too deep here. LOL


 

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7 hours ago, BobWill said:

4    Internal Cast    (original inner surface dissolves and space fills with solidifying material)

 

Bob, you still don't have it.  When the "original inner surface dissolves" it exposes the outer surface.  A cast of the exterior of the fossil is an external cast by your own (#3) definition.  I gave you the logical correction earlier.

http://pristis.wix.com/the-demijohn-page

 

What seest thou else

In the dark backward and abysm of time?

---Shakespeare, The Tempest

 

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5 hours ago, Harry Pristis said:

 

Bob, you still don't have it.  When the "original inner surface dissolves" it exposes the outer surface.  A cast of the exterior of the fossil is an external cast by your own (#3) definition.  I gave you the logical correction earlier.

Of course I could have this wrong but this is the way I have learned these terms. I will present my explanation with reference numbers so we can discuss this "by the numbers" to make it easier.

 

1. If a space is available to fill when the shell dissolves then that means there is material I will call material X, which can be in place on both sides of the shell  before it dissolves. Material X is able to form a copy of the original which makes it a mold.

 

2. In the case of one valve of a bivalve this can be an external mold (able to duplicate the external surface) or an internal mold (able to duplicate the internal surface).

 

3. The material that fills the space where the shell was I will call material Y. When material Y solidifies it forms a copy of the original which makes it a cast.  If material Y is then exposed when the material X erodes away it is either an external or internal cast depending on which surface is exposed.

 

4. If that cast is of the original inner surface then it is an internal cast. If it is of the outer surface it is an external cast. They may both be present or either one may have also dissolved away.

 

5. An internal cast is only likely to become exposed with something like a single valve of a bivalve because otherwise a cast would only show the outer surface. It is possible to find a fossil of a single valve showing the inner (usually concave) surface which has been duplicated in this way.

 

Interestingly I have this fossil of an Idiohamites where most of the fossil is an external mold. There are places along the fossil where there is a duplicated piece of the original shell attached to the mold with one side broken away revealing pieces of the concave inner surface of the original shell. I would call those parts internal casts.

 

idiohamites.jpg.9c5ac06eac20c90f6a60db6fd588a587.jpg

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Great topic.

I wonder if compression is that closely connected to carbonization?

at least in (geologist-) German it just means a fossil that is preserved in a very flattened way. Carbonisation on the other hand may in some cases happen with perfect 3d structure. They do appear together in some famous cases though.

 

I am also not sure if desiccation (drying) applies to permafrost fossils. What they do have in common is the preservation of organic substance.

 

Best Regards,

J

Try to learn something about everything and everything about something

Thomas Henry Huxley

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I think that I understand what Bob is trying to say about the definitions of casts and molds. It can be better shown with labeled diagrams.

 

Good definitions of cast and mold along with a diagram hopefully will prevent any confusion between internal casts and internal molds. 

1274F163-A596-4224-BBE0-C3D778755354.jpeg

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My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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47 minutes ago, Mahnmut said:

Great topic.

I wonder if compression is that closely connected to carbonization?

 

I am also not sure if desiccation (drying) applies to permafrost fossils. What they do have in common is the preservation of organic substance.

Carbonized fossils are often compressed because carbon is not very hard unlike silicified fossils.

 

Fossils in permafrost can be desiccated (dried out) especially when they were dried out before being buried. Have you heard of freeze drying?

My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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49 minutes ago, DPS Ammonite said:

Carbonized fossils are often compressed because carbon is not very hard unlike silicified fossils.

 

Fossils in permafrost can be desiccated (dried out) especially when they were dried out before being buried. Have you heard of freeze drying?

Of course you are right, both pairs (compression/carbonisation and permafrost/desiccation do often occur together. I just wanted to say that they are not the same or subgroups of one another. there are compressed fossils without a trace of carbon left, there are 3d fossil in carbon, there are also frozen remains in permafrost that are not much desiccated and do decay rapidly after thawing.

Best regards,

J

Try to learn something about everything and everything about something

Thomas Henry Huxley

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First time I really understand cast and mold - got it totally wrong until now! Thanks, @BobWill and @DPS Ammonite!

 

As already stated by @Mahnmut, coalified organic matter (esp. wood) can be compressed or not, sometimes side by side.

 

But do I really miss something? Maybe I have overlooked it:

What about preservation of the original skeletal material? I am thinking about calcitic oyster shells or calcitic, fibrous/prismatic Pinna shells. Isn´t  sometimes the structure of the calcite (grain size, grain shape etc.) perfectly preserved? And what about crinoid fragments? They are often still the same singe calcite crystal as they used to be during life time. Aren´t they?

 

Franz Bernhard

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1 hour ago, FranzBernhard said:

First time I really understand cast and mold - got it totally wrong until now! Thanks, @BobWill and @DPS Ammonite!

 

But do I really miss something? Maybe I have overlooked it:

What about preservation of the original skeletal material? I am thinking about calcitic oyster shells or calcitic, fibrous/prismatic Pinna shells. Isn´t  sometimes the structure of the calcite (grain size, grain shape etc.) perfectly preserved.

 

Franz Bernhard

Any remains of organisms are fossils as long as they are older than about 10k years. They can be essentially unchanged. I mentioned that to Bob yesterday as a category of fossils: unchanged. Sometimes the organisms are so well preserved than they come back to life.

Many/most creationists define “fossils” as being changed or transformed from their original material and not by their 10k year age. Creationists use the fact that wood can be petrified rapidly in the lab and hot springs with lots of silica as evidence that “fossils” can be younger than the less than 10k year age of the Earth.

 

@FranzBernhard  I am glad that we helped you understand what casts and molds are. I have talked to professional geologists and paleontologists that did not know. What did you think steinkerns were in the past; molds or casts? 

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My goal is to leave no stone or fossil unturned.   

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Thanks for all the help folks! This is still a work in progress so don't hesitate to offer more ideas. Keep in mind that although it began as a reminder list for me when I give fossil talks, the version here is intended to add to material we pass out to the public when the Dallas Paleontological Society appears at shows and related events for educational purposes. For that reason I would like the definitions to be as concise as possible so they will fit on one line of text. I also have had to reduce the font to 10 to get it all on one page. However, I do not want the criteria to cause omissions or confusion.

 

John, when you reminded me about unchanged material I asked if they would be considered to have undergone "fossilization" even though they are certainly fossils in the broadest sense. That term suggests a process rather than just a state of being so I wanted to be precise. I could change the title to reflect that subtle nuance if it would matter for adding it to the list. This is something I had not considered before.

 

I have also heard that not everyone agrees with the cut-off at 10k years. While some use the end of the Pleistocene Epoch at 11k, others have pointed out that material can begin to mineralize even sooner so that might be considered fossilization. I have heard the argument for creation based on this idea but it fails for other reasons as well.

 

Thanks @Mahnmut and @DPS Ammonite for the additional information about compression, coalification and carbonization. Do either of you think there is a change I could make to reflect your input or is it okay like it is?

 

I agree that more detail and even images would help people understand the scientific terminology easier but to keep it simple and to encourage personal inquiry I decided on simplicity. Please feel free to use or alter the list any way you like for any purpose. No need to credit me since I have gotten lots of help form many textbooks, personal conversations and e-comments.

 

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Perhaps add in a sentence that combinations of the mentioned principles are possible or even normal?

Impressive list!

Cheers,

J

 

 

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Try to learn something about everything and everything about something

Thomas Henry Huxley

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Bob said, “For that reason I would like the definitions to be as concise as possible so they will fit on one line of text. I also have had to reduce the font to 10 to get it all on one page.“

 

My reply: consider making multiple columns on a page. Have one line for casts, internal and external. Same with molds. Print on legal sized paper.

 
Bob said, “I have also heard that not everyone agrees with the cut-off at 10k years. While some use the end of the Pleistocene Epoch at 11k, others have pointed out that material can begin to mineralize even sooner so that might be considered fossilization.”
 
My reply: define a fossil. You can put a range of accepted dates: 10-11k. I guess that fossilization is a process of change that can continue even after remains officially become a fossil around 10k years. Just because something is mineralized doesn’t mean that it is a fossil. It has to be old too.
 

I still think that diagrams like the crude hand drawn ones (fixed up of course) that I posted a few hours ago would be very helpful to show what casts and molds are.

 

Also, your title needs to reflect that you sort of have a hybrid list. Types of fossils and methods of fossilization.

 

If you create a formatted one page list we will look at it and give our comments.

 

 

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My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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3 hours ago, DPS Ammonite said:

Sometimes the organisms are so well preserved than they come back to life.

I have heard about bacteria in salt rocks. Is this real or a hoax?

 

3 hours ago, DPS Ammonite said:

I mentioned that to Bob yesterday as a category of fossils: unchanged.

Thanks! I missed that!

 

3 hours ago, DPS Ammonite said:

What did you think steinkerns were in the past; molds or casts? 

Casts! With the inner surface of the fossil as the mold....

But the definition given in this thread is perfectly logical from a casters/founders point of view:

- The fossil is the original object.

- Everything getting its shape from this original object is a mold, irrespective if its the inner or outer surface of the original object. However, a caster/founder could have some troubles getting an internal mold of a (nearly) closed original object without destroying this object.

- Everything that has the shape of the original fossil is a cast (These "real" casts seem not to be super-abundant in nature?).

 

Franz Bernhard

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12 minutes ago, FranzBernhard said:

- Everything that has the shape of the original fossil is a cast (These "real" casts seem not to be super-abundant in nature?).

I am glad that I converted you to the truth.
 

Come to Arizona. We have lots of Paleozoic silicified fossils that are casts. I have gone through many gallons of acid trying to dissolve them out of limestone.

 

Also, I think that the story about the ancient revived bacteria is true:

https://www.cbsnews.com/news/bacteria-250-million-years-young/

 

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My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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26 minutes ago, FranzBernhard said:

 

However, a caster/founder could have some troubles getting an internal mold of a (nearly) closed original object without destroying this object.

Franz Bernhard

I think this is why so many people have trouble calling a  steinkern an internal mold. I had trouble with this at first and you can frequently see people getting it wrong on Youtube and other places. The important thing for me is that you will not see it wrong in a peer reviewed journal and we should strive to use good scientific terms to avoid confusion.

 

Their abundance in the fossil record shows up here in north Texas where most of the ammonites, for example, are internal molds because they show the sutures.

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17 minutes ago, DPS Ammonite said:

We have lots of Paleozoic silicified fossils that are casts.

You are using the word "silicified", which implies replacement to me. A cast would be dissolution of a shell and later infill of the resulting void with silica precipitated from a solution.

Franz Bernhard

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12 minutes ago, BobWill said:

I think this is why so many people have trouble calling a  steinkern an internal mold.

That was my problem, too! :D

And that´s why the term "Steinkern" was invented! ;)

Franz Bernhard

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19 minutes ago, FranzBernhard said:

You are using the word "silicified", which implies replacement to me. A cast would be dissolution of a shell and later infill of the resulting void with silica precipitated from a solution.

Franz Bernhard

Casts can be created in different ways. The original organism’s hard part can be dissolved away leaving a void that is later filled by a material. The original hard part can also be replaced but by bit by silica where a large void is never created. A cast can also be created when a material such as calcium carbonate of a shell recrystallizes into  larger crystals.

My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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2 hours ago, Harry Pristis said:

Good grief!  A steinkern is NOT any kind of mold.  It is a cast.  A mold is empty; a cast is the filling.

Back to scratch? 

 

2 hours ago, Harry Pristis said:

A mold is empty; a cast is the filling.

Sure you can define it in that way.

 

But also in that way:

3 hours ago, FranzBernhard said:

But the definition given in this thread is perfectly logical from a casters/founders point of view:

- The fossil is the original object.

- Everything getting its shape from this original object is a mold, irrespective if its the inner or outer surface of the original object. However, a caster/founder could have some troubles getting an internal mold of a (nearly) closed original object without destroying this object.

- Everything that has the shape of the original fossil is a cast

Franz Bernhard

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