A relative age is the age of a fossil organism, rock, or geologic feature or event defined relative to other organisms, rocks, or features or events rather than in terms of years.Tradition paleontological and biostratigraphic correlation methods are still perhaps the most common relative dating methods used by geologists.Geologic research and mapping requires the determinations of the ages and composition of rocks.
Paleontology is the study of life in past geologic periods (fossil plants and animals), incorporating knowledge of an organism's phylogeny, relationships to existing organisms, and correlation to an established chronology of Earth History.
Paleontology is limited to the study of sedimentary deposits where fossils are preserved, but can be used in establish relative ages of nearby igneous intrusion, faults, and other geologic features.
This is because new sediments are always laid down on top of sediments that have already been deposited.
So, when looking at the history of a cliff face, it is important to read the story it tells from the bottom layer up.
The sediment of this area was laid down after ammonite A appeared 199 million years ago, and before ammonite B became extinct 195 million years ago.
This narrows the date of the delta beds to the four million years between these dates.
Typically, paleontological information is used in conjunction with other methods of relative or absolute age dating.
The most important tools for paleontologists are collections of fossils and paleontological reports (with fossil plates for identification) from other locations in the region or around the world.
The second method is called absolute dating and is done by analysing the amount of radioactive decay in the minerals of the rocks.