Petrified Bone Date??
8 messages in this thread
I've just joined this forum temporarily to get an answer to a basic question
regarding the approximate age of a sample of pertified bone.
We have a large, petrified back bone that measures about four inches across.
The linear section (broken at both ends) is about six inches long. In the
center of the length, is a vertabrae where the bone joined. On the inside is a
yellowish marrow material. All of this is sold rock or quartz-like material.
We wanted to know over what kind of time frame does an organic material, like
bone, turn into a pertrified rock or quartz material? I kind of understand
how petrification works, in that soluble minerals infiltrate the organic
material, and over time they crytallize. But over what kind of time frame?
Note: The specimen was found in a rocky creek bottom, about five miles from a
major river, in the middle of a 3,000 + acre privately-owned pine timber forest
in South Alabama. There are numerous pieces of petrified wood in this same
creek bottom.
If you can give a slightly more precise location, you might be able to find
someone here who has a bedrock map of Alabama who could pinpoint its age. Or,
check with the Alabama department of natural resources. They'll have bedrock
maps of the state for sale for less than $10, I'm sure.
Next time you're there, collect a few bushel baskets of this stuff! It's only
going to rot in the stream, or in the next rainstorm.
The petrified bone was found in Clarke County, Alabama in the stream bed of
Silver Creek, near Silver Creek Falls (a natural water falls, about 12-15 in
height, about five miles upstream of the Alabama River). However, I fail to
understand how a bedrock map could indicate the age of a petrified bone sample
found in a fast flowing stream. Again, my general question is, what range of
time is necessary for organic molecules, like bone or wood, to turn into an
inorganic material, such as petrified bone or wood?
As for your comment about the stuff 'rotting', that would be impossible, since
it is pure rock or quartz. It could wear away over a long period, but not
decompose or 'rot'.
The bedrock map helps tell when the rock that enclosed the bone was laid down.
Actually, if it's a dino bone, we can nail down the time period to a few
hundred million years, if that's close enough for you. 🙂 For "rotting",
yes, the weather will split those rocks eventually. Some dino bones will "rot"
in a single season, but there can be a lot of variation. How long did it take
for bone to turn to stone? That's a better question I'll leave for someone
more expert than I.
If the sample bone is a dinosaur bone, then it would be impossible for it to be
a 'few hundred million years old (a few meaning three or more), since it is
estimated that dinosaurs roamed this planet between 65 and 230 or so million
years ago. :-<
Picky, picky! 🙂 What, is this the English Forum? There's mile-long threads
here about interloper planets and the Earth cracking and splitting, but you're
picking on the word "few"?
On a more serious note, I'd guess we could put a thumbnail estimate on the
length of time it takes for bone to petrify… order of magnitude, more than
100,000 years, no? But I'm sure there are conditions under which a bone could
be mineralized in a matter of decades, too.
Hi, John–
Welcome to the forum!
I am an amateur mineral collector, but there are others here who know more
about fossils. For their benefit, can you say anything about the rock
containing the fossils? Given the location and some notion of the enclosing
rock, someone may be able to match that rock to an upstream formation and give
an estimate of its age. The location might be enough if there is only one
dino-bearing rock formation upstream.
How long it takes something to fossilize surely depends on the minerals
involved, among other things. Gypsum crystals can grow in months, sometimes to
enclose modern artifacts, but quartz requires thousands or millions of years to
form, at least in geodes. I am guessing calcite might replace something much
faster than quartz.
Fossils cannot literally "rot", but John was using the word in a figurative
sense. Fossils left there will likely be eroded to uselessness within a few
years, depending on how tough their composition is. Even if made of a tough
mineral, the cohesion between separate parts of the fossil may not be great, so
fossils are generally less durable than rocks. This means a fossil could not
easily travel far from its home formation, though one cannot be really sure
without radioactive dating, sure species or host rock identification, or some
such.
–Doug
The first steps of fossilization probably often happen very quickly, or the
bone would just rot away (exceptions occur in certain oxygen free environments,
etc). After that, continued mineralization may continue for a very long time,
thousands or millions of years.
Sounds like you've got an interesting fossil. You ought to bring it to a
museum or university and somebody there may be able to tell you what it is!
Cheers,
GTL
– Greg Laden, Written 26-Sep-1994 @ 20:09:03
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