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Author Topic: What conditions are required for a fossil to form?  (Read 29185 times)

Arturo Pulecio

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Arturo Pulecio asked the Naked Scientists:

I wonder what the conditions need to be to achieve fossilisation?

Why can things like  dinosaur footprints on the sand, flowering plants and soft bodied micro-organisms be fossilised rather than rot and fade away like the things we see daily? If corpses and trees regularly decay and get reabsorbed, what makes those other specimens different? Will current organisms fossilise?


What do you think?


 

Offline JimBob

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What conditions are required for a fossil to form?
« Reply #1 on: 17/05/2008 00:39:05 »
The most important step in fossil formation is rapid burial - before the hard parts are either eaten or dissolved. In may places this doesn't take long at all. A bone can be dissolved in a couple of months or it can be eaten in a day or two in most environments. Mud is the best thing to wash in and cover the critter to become a fossil but sand will also work under most conditions. Then, it can't be eroded away at any time in the future after it is buried.

Next, it needs to be deeply buried and turned to rock - well sort of rock. Along the coast it can be deposits of fairly recent age - 10,000 years or so - and there cannot be any chemicals travel through the rock that will destroy the fossil as the rock solidifies. The process of solidification and small chemical changes that welds the parts together to make a rock is called diagenesis. This diagenesis also forms and solidifies the fossil itself, no matter what it is.

THEN - after it is a rock, it needs to be found so you can hold the fossil! Hope this helps. If you need anything clarified just ask.

« Last Edit: 17/05/2008 15:22:28 by JimBob »
 

Offline chris

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What conditions are required for a fossil to form?
« Reply #2 on: 17/05/2008 12:30:31 »
That's really interesting, thanks JimBob. But returning to the point raised by Arturo in his question, what about footprints? How do they re-emerged as formed prints? What happens to the rock that forms above them?

Chris
 

Offline JimBob

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What conditions are required for a fossil to form?
« Reply #3 on: 17/05/2008 15:25:30 »
The fossil is found due to the process by which all other fossils are revealed - erosion. The overlying sediments are stripped away. A foot print, a leaf or any other fossil needs to have some erosion involved in bringing it back to the surface so it can be found.
 

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What conditions are required for a fossil to form?
« Reply #3 on: 17/05/2008 15:25:30 »

 

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