The two approaches are often complementary, as when a sequence of occurrences in one context can be correlated with an absolute chronlogy elsewhere.Local relationships on a single outcrop or archaeological site can often be interpreted to deduce the sequence in which the materials were assembled.Episodes of global volcanic activity, rifting of continents, folding, and metamorphism are defined by absolute ages.The results suggest that the present-day global tectonic scheme was operative in the distant past as well.Using this established record, geologists have been able to piece together events over the past 635 million years, or about one-eighth of Earth history, during which time useful fossils have been abundant.
When these regions are later exposed in uptilted portions of ancient continents, a history of terrestrial rock-forming events can be deduced.
Dating, in geology, determining a chronology or calendar of events in the history of Earth, using to a large degree the evidence of organic evolution in the sedimentary rocks accumulated through geologic time in marine and continental environments.
To date past events, processes, formations, and fossil organisms, geologists employ a variety of techniques.
The same margin of error applies for younger fossiliferous rocks, making absolute dating comparable in precision to that attained using fossils.
To achieve this precision, geochronologists have had to develop the ability to isolate certain high-quality minerals that can be shown to have remained closed to migration of the radioactive parent atoms they contain and the daughter atoms formed by radioactive decay over billions of years of geologic time.
Without absolute ages, investigators could only determine which fossil organisms lived at the same time and the relative order of their appearance in the correlated sedimentary rock record.