There are two main methods determining a fossils age, relative dating and absolute dating.
Because radiocarbon has a half-life of 5,730 years—that is, it takes 5,730 years for half a sample of radiocarbon to decay—it is ostensibly possible to accurately determine the age of a thing by looking at the amount of radiocarbon it contains.
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?
This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.
These use radioactive minerals in rocks as geological clocks.