In this relative dating method, Latin terms ante quem and post quem are usually used to indicate both the oldest and the most recent possible moments when an event occurred or an artifact was left in a stratum.But this method is also useful in many other disciplines.The rate at which racemization proceeds depends on the type of amino acid and on the average temperature, humidity, acidity (p H), and other characteristics of the enclosing matrix.Also, D/L concentration thresholds appear to occur as sudden decreases in the rate of racemization.Biostratigraphy does not directly provide an absolute age determination of a rock, but merely places it within an interval of time at which that fossil assemblage is known to have coexisted.Both disciplines work together hand in hand however, to the point where they share the same system of naming rock layers and the time spans utilized to classify layers within a stratum.
This usually requires what is commonly known as a "dating method".
The science of geochronology is the prime tool used in the discipline of chronostratigraphy, which attempts to derive absolute age dates for all fossil assemblages and determine the geologic history of the Earth and extraterrestrial bodies.
By measuring the amount of radioactive decay of a radioactive isotope with a known half-life, geologists can establish the absolute age of the parent material.
This means that the amino acid can have two different configurations, "D" or "L" which are mirror images of each other.
With a few important exceptions, living organisms keep all their amino acids in the "L" configuration.