How Young Can a True Fossil Be?

[dolphinboy]

If I was digging in a fossil-rich area, and I found a fossil, I would assume it was ancient, but obviously fossils can be very old, old or not-so-old.

So assuming the conditions are right for fossilization, how quickly can something fossilize? A few hundred years? A few thousand years? Or are all fossils by definition at least 10,000 (input you number here) years old?

Make any assumptions you want about sediment type, weather conditions or volcanic activity you wish.

[awldune]

I think it depends on your definition of fossil, but the process of permineralization (think dinosaur bones) is generally understood to require about 10,000 years.

[John Mace]

I think you're confusing "fossilize" with "petrify", although I see the dictionary seems to consider them synonyms.

Just keep in mind that any artifact, even an impression in the earth, can be a fossil, whether it has petrified or not.

[dolphinboy]

Originally Posted by John Mace

I think you're confusing "fossilize" with "petrify", although I see the dictionary seems to consider them synonyms.

Just keep in mind that any artifact, even an impression in the earth, can be a fossil, whether it has petrified or not.

For the sake of this thread let's assume we are talking about normal animal bones. If an animal dies under the right conditions it's bones will fossilize over time, or so I have been told. How long does that process take at a minimum?

[John Mace]

Originally Posted by dolphinboy

For the sake of this thread let's assume we are talking about normal animal bones. If an animal dies under the right conditions it's bones will fossilize over time, or so I have been told. How long does that process take at a minimum?

I don't know the answer, but it's going to depend on the size of the bone, the environment and the temperature and humidity at the very least.

[TriPolar]

I'm 56 and I've been called a fossil. So compared to dinosaur bones, that's not a long time.

[John DiFool]

At a school I went to once I would discover impression fossils of various shells in an open field. I later realized that they were indeed impressions, but of very recent vintage, made in the chalky slurry they used to "pave" the place (it was in the sticks, yes) which also contained various shells.

[Askance]

Originally Posted by dolphinboy

For the sake of this thread let's assume we are talking about normal animal bones. If an animal dies under the right conditions it's bones will fossilize over time, or so I have been told. How long does that process take at a minimum?

I think what JM is trying to say is that any preserved remains of animals or plants (or even just impressions of them) are called fossils. Consequently it takes as long as burying a bone does, although Wikipedia says that the term is only applied to anything older than an arbitrary 10,000 years.

Probably what you are actually asking is how long before they get mineralised, that is the organic matter replaced with inorganic while still preserving the structure. I know there are opal mines in Australia where the pit props are being turned into opal, so that would be under 200 years.

[gazpacho]

Cecil has a column addressing this.

http://www.straightdope.com/columns/...elf-fossilized

He says a couple of centuries but that is said in a joking manor so I assume it is not well researched.

[Enola Straight]

Place a leaf from a tree on wet cement.

Remove leaf when cement has fully set.




Is the leaf impression in the cement a fossil?



I remember the cover of a National Geographic where an early hominid was crossing a freshly "ashed" ground after a volcano eruption...and the footprints in the ash solidified like cement.

The footprints were considered "fossils"...must the process be entirely natural and not have a man-made/artificial/synthetic element?

[Chronos]

There's a bat in Lewis and Clark Caverns that is completely encased in a thin layer of fresh limestone. IIRC, it's less than a century old.

And even if most of a bone or other relic is replaced with inorganic material, that doesn't mean all of it has. They've actually found soft tissues still extant in T. rex bones.