Absolute radiometric dating
Similarly, in geologic studies, vast quantities of information from widely spaced outcrops have to be integrated.Some method of correlating rock units must be found.Chronometric techniques include radiometric dating and radio-carbon dating, which both determine the age of materials through the decay of their radioactive elements; dendrochronology, which dates events and environmental conditions by studying tree growth rings; fluorine testing, which dates bones by calculating their fluorine content; pollen analysis, which identifies the number and type of pollen in a sample to place it in the correct historical period; and thermoluminescence, which dates ceramic materials by measuring their stored energy.
Although with clever detective work many complex time sequences or relative ages can be deduced, the ability to show that objects at two separated sites were formed at the same time requires additional information.
In the ideal case, the geologist will discover a single rock unit with a unique collection of easily observed attributes called a marker horizon that can be found at widely spaced localities.
Any feature, including colour variations, textures, fossil content, mineralogy, or any unusual combinations of these can be used.
Just as the use of the fossil record has allowed a precise definition of geologic processes in approximately the past 600 million years, absolute ages allow correlations back to Earth’s oldest known rocks formed more than 4 billion years ago.
In fact, even in younger rocks, absolute dating is the only way that the fossil record can be calibrated.
Search for absolute radiometric dating:
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.