Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it.
In the past, the outcrop has been quarried frequently for iron ore or building stone.
The Wheeler Formation has been previously dated to approximately 507 million year old, so we know the trilobite is also about 507 million years old.
But, how can we determine how old a rock formation is, if it hasn’t previously been dated?
When organisms die, C-14 decays and is not replaced.
Since we know the concentration of radioactive carbon in the atmosphere, and we also know that it takes 5,730 years for half of C-14 to decay (called a “half-life cycle”), and another 5,730 years for half of what’s left to decay, and so on, by measuring the remaining concentration of radiocarbon we can tell how long ago an organism died.