Definition of absolute dating of fossils
we often make reference to fossils to explain the past of living beings. Fossils are remnants (complete or partial) of living beings that have lived in the past (thousands, millions of years) or traces of their activity that are preserved generally in sedimentary rocks. Have you ever wondered how science knows the age of a fossil? If you think of a fossil, surely the first thing that comes to your mind is a dinosaur bone or a petrified shell that you found in the forest, but a fossil is much more.The half-lives of several radioactive isotopes are known and are used often to figure out the age of newly found fossils.Different isotopes have different half-lives and sometimes more than one present isotope can be used to get an even more specific age of a fossil.Relative dating is achieved by determining the position of rock in strata, and the appearance of certain index fossils.Relative dating was a precursor to absolute dating.
The ESR (electro spin resonance) involves irradiating the sample and measuring the energy absorbed by the sample depending on the amount of natural radiation which it has been subjected during its history.
The oldes tknown fossils are The magnetic north pole has changed throughout the history of Earth and its geographical coordinates are known in different geological eras.
Some minerals have magnetic properties and are directed towards the north magnetic pole when in aqueous suspension, for example clays.
As radioactive isotopes of elements decay, they lose their radioactivity and become a brand new element known as a daughter isotope.
By measuring the ratio of the amount of the original radioactive element to the daughter isotope, scientists can determine how many half-lives the element has undergone and from there can figure out the absolute age of the sample.
It is a complex method which you can get more information here.