Things have been documented to petrify within several decades or faster in lab conditions.
As is now well known, wood can petrify rapidly. Several laboratory experiments have devised ways in which this can be done, mirroring natural settings. (See Sigleo, 1978 "Organic Geochemistry of Silicified Wood," Geochimica et Cosmochimica Acta, vol. 42, pp. 1397-1405, and Leo and Barghoorn, 1976, "Silicification of Wood," Botanical Museum Leaflets, vol. 25, no. 1, Harvard University, 47 pp.)
http://www.icr.org/article/how-long-does-it-take-for-wood-petrify/
So I guess I don't understand the question... why must we exclude the flood for fossils??? There was plenty of time for them to form.
If you are going by radioactive decay rates, first you have to explain from physics why a given element has a decay rate vs. just any rate of decay, so you can trust the basis upon which you are calculating the rate of decay. Observing a rate of decay that has been consistent for 100 years, is insufficient to prove the decay rate has not varied at all points in human history.
In the past scientists have argued that under no conditions can the rate of radioactive decay change, and so when they applied it to fossil research, they erroneously told us it was proven constant (it wasn't proven), and that this could then be used to extrapolate into the past with proven accuracy.
However, science has recently demonstrated that decay rates are not constant, as they have observed variances due to the sun in some elements but not all elements.
And while certainly we can try to date with the elements we do not observe changes, or we can assume that the differences in the elements which do have varying rates of decay, that these differences would not affect dating... but this is called an assumption, it is not called proven science.
At the core of the problem is the ambiguity which causes the rate of decay. No one knows what causes it on a physical science level where they can give you formulas that explain what the particles are doing which cause the varying decay rates. Meaning, they do not know with absolute certainty, under what conditions decay rates would vary. We view that they change with proximity to the sun, but do they also change with other phenomena found throughout the universe? Does the universe itself have changing decay rates built into it's structure?
They couldn't tell you, because they couldn't tell you how it happens in the first place.
Therefore, all radioactive dating is a lot of guess work based on assumptions we have no reason to believe in and of themselves.