What is absolute carbon dating of fossils
This then can be used to deduce the sequence of events and processes that took place or the history of that brief period of time as recorded in the rocks or soil.For example, the presence of recycled bricks at an archaeological site indicates the sequence in which the structures were built.Similarly, in geology, if distinctive granitic pebbles can be found in the sediment beside a similar granitic body, it can be inferred that the granite, after cooling, had been uplifted and eroded and therefore was not injected into the adjacent rock sequence.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.The same margin of error applies for younger fossiliferous rocks, making absolute dating comparable in precision to that attained using fossils.
Unlike ages derived from fossils, which occur only in sedimentary rocks, absolute ages are obtained from minerals that grow as liquid rock bodies cool at or below the surface.
In addition, they have had to develop special techniques with which to dissolve these highly refractory minerals without contaminating the small amount (about one-billionth of a gram) of contained lead and uranium on which the age must be calculated.
Since parent uranium atoms change into daughter atoms with time at a known rate, their relative abundance leads directly to the absolute age of the host mineral.
It is only by correlations that the conditions on different parts of Earth at any particular stage in its history can be deduced.
In addition, because sediment deposition is not continuous and much rock material has been removed by erosion, the fossil record from many localities has to be integrated before a complete picture of the evolution of life on Earth can be assembled.