Radiometric dating uranium 235
The radioactive isotope Carbon 14 has a half-life of 5,730 years.
This has made it useful for measuring prehistory and events occurring within the past 35 to 50 thousand years.
So a 40,000 year C-14 date and a 60,000 year thermoluminescence date could easily come from the same strata, right next to each other, and possibly reflect a date of anything between 30,000 and 70,000 calendar years depending on the standard deviations of your dates.
Some thermoluminescence dates that are in the order of 50,000 years /- 25,000 years, which with a two standard deviation limit puts it anywhere between yesterday and 100,000 years ago.
These unstable atoms tend to "decay" into stable ones; they do this by emitting a particle or particles. The time it takes for half of a given amount of a radioactive element to decay into a stable one is what is known as the "half-life".
By matching the proportion of original unstable isotope to stable decay product, and knowing the half-life of that element, one can thus deduce the age of the rock, as shown in the following diagram.
Volcanic tuft containing U-235 also contains (stable) Lead associated directly with it.
However, although 5730 years is the correct half-life, it is not the one used for most C-14 dating, simply because the original half-life used to determine dates back in the 1950s was wrong, and to be consistent we still tend to use the wrong value (a bit like the direction of current flow in electronics, which is the opposite of that which the electrons take, but was the original and incorrect assumption).
The practical range for dating is in the order of a few hundred to about 40,000 years BP.
Here are the half-lives of some other radioactive elements: These are said to be used in dating techniques of gas formation light emission called thermoluminescence).
Besides thermoluminescence there is also the measurement of the ratio of the radioactive material to its decay elements.