Imagine that a layer of leaves is scattered along a forest floor; what must happen in order to preserve these leaves as fossils?

For the leaves to be presearved as fossil, they have to undergo a natural process of carbonization. This involves a slow chemical reaction with water over time that allows oxygen, nitrogen, and hydrogen to escape the leaves’ structure as gases leaving behind a carbon skeleton/film.

To preserve the leaves that are put in a forest floor the leaves have to be dehydrated and put in 10% formalin.

Explanation:

The tissues or any organelles that are got form any organism contains a lot of hydration in them; it is the water content that makes them vulnerable to contamination.

In order for the leaves to remain like fossils, they must be naturally carbonated. This involves a slow chemical reaction with water, allowing oxygen, nitrogen and hydrogen to escape from the leaf structure as the gas leaves the carbon atoms.  

The contamination is caused by the bacteria that grow on these leaves by feeding on the hydration and organic content of the material, when this is fixed using an organic solvent then there is no room for contamination.

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.