Wiens has a Ph D in Physics, with a minor in Geology.
His Ph D thesis was on isotope ratios in meteorites, including surface exposure dating.
Then after another 5,000 years half of the remaining parent isotope will have decayed.
But, how can we determine how old a rock formation is, if it hasn’t previously been dated?
There are two main methods determining a fossils age, relative dating and absolute dating.