The deeper layers are older than the layers found at the top, which aids in determining the relative age of fossils found within the strata. Such index fossils must be distinctive, globally distributed, and occupy a short time range to be useful.
Geologists often need to know the age of material that they find.
They use absolute dating methods, sometimes called numerical dating, to give rocks an actual date, or date range, in number of years.
This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.
Before the advent of absolute dating methods in the twentieth century, nearly all dating was relative.Similarly, pollen grains released by seed-bearing plants became fossilized in rock layers.Carbon dating is used to determine the age of biological artifacts up to 50,000 years old.He holds a Bachelor of Science, postgraduate diplomas in journalism and website design and is studying for an MBA.Paleontology seeks to map out how life evolved across geologic time.Because rock sequences are not continuous, but may be broken up by faults or periods of erosion, it is difficult to match up rock beds that are not directly adjacent.