In this article we shall discuss how fossils can be used for the purposes of absolute dating.
We have already discussed the construction of the geological column.
In this case, the use of fossils will be absolutely the best method available.
Second, it is much faster than any more technical method.
For example, suppose that using stratigraphic methods, we can show that a particular fossil is always older than rocks which are 14 million years old or less, and always younger than rocks which are 16 million years old or more, whenever we are in a position to make a comparison.
Now, it is a fundamental principle of science — arguably, the only fundamental principle of science — that a rule that works every time we can test it must be taken as true unless and until we find a counterexample.
The two approaches are often complementary, as when a sequence of occurrences in one context can be correlated with an absolute chronlogy elsewhere.
Hence we can use datable rocks to put dates on fossil species; and then we can use the fossil species to put dates on other rocks which would otherwise be difficult to date.
Those fossils we have described as "index fossils" are particularly suitable for this purpose, since they have a wide geographical distribution but only inhabit a thin slice of time.
Radiometric dating is used to estimate the age of rocks and other objects based on the fixed decay rate of radioactive isotopes.
Learn about half-life and how it is used in different dating methods, such as uranium-lead dating and radiocarbon dating, in this video lesson. We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 2,000 colleges and universities.