Fibres and cellular structures preserved in 75-million–year-old dinosaur specimens

Nature Communications ^ | 09 June 2015 | Sergio Bertazzo, Susannah C. R. Maidment, Charalambos Kallepitis, Sarah Fearn, Molly M. Stevens

[BroJoeK]

Sopater: "What I do dispute is that anyone can know for certain what the original amount of the daughter atoms were when the rock was formed, and if any of the parent or daughter atoms have been added or removed due to some natural environmental condition during that time."

That radioactive "clocks" are "set" to zero can be tested and confirmed by comparing results of known young material to that of known older material.
Yes, I know, there is a whole underworld of junk-science out there, which claims material from Mount St. Helens was "tested" at millions of years old.
But that's a fraud, a fake, not legitimate tests.

As I posted before: radiometric testing is tricky at best, easy to do wrong, and in need of frequent check and recheck.
As I said, labs which do this stuff for a living well know how to do it wrong, and what is necessary to get it right.

So whenever we see insane results -- such as Mount St. Helens' material millions of years old, or dinosaurs just a few thousand years old -- we know that something went seriously wrong, and that results should be rejected out of hand, until or unless thorough review and repeating by highly knowledgeable people confirms them.

But the bottom line is that there are so many different processes (dozens) which can be used to date geological materials, each with its own range of datable half-lives, each overlapping the others at various time-scales, and each able to confirm results achieved by some of the others.
I don't think it's possible that all those methods would produce consistent, but nevertheless false dating.

For a simple but thorough primer, you might consider this.

[Sopater]

You can measure with amazing precision that your “clock” is counting years, days, hours, minutes, and seconds with little or no error. However, if you don’t actually know what year, month, and day it is, you will have some difficulty in actually setting your clock correctly.

[BroJoeK]

Sopater: "However, if you don’t actually know what year, month, and day it is, you will have some difficulty in actually setting your clock correctly."

But all such measurements are from today back to the time of "closure".

Here is what the above link says on that subject:

"If a material that selectively rejects the daughter nuclide is heated, any daughter nuclides that have been accumulated over time will be lost through diffusion, setting the isotopic "clock" to zero.
The temperature at which this happens is known as the closure temperature or blocking temperature and is specific to a particular material and isotopic system.
These temperatures are experimentally determined in the lab by artificially resetting sample minerals using a high-temperature furnace.

As the mineral cools, the crystal structure begins to form and diffusion of isotopes is less easy.
At a certain temperature, the crystal structure has formed sufficiently to prevent diffusion of isotopes.
This temperature is what is known as closure temperature and represents the temperature below which the mineral is a closed system to isotopes.

Thus an igneous or metamorphic rock or melt, which is slowly cooling, does not begin to exhibit measurable radioactive decay until it cools below the closure temperature.

The age that can be calculated by radiometric dating is thus the time at which the rock or mineral cooled to closure temperature.[11][12]

Dating of different minerals and/or isotope systems (with differing closure temperatures) within the same rock can therefore enable the tracking of the thermal history of the rock in question with time, and thus the history of metamorphic events may become known in detail.
This field is known as thermochronology or thermochronometry."