Radioactive age dating equation
To serve as geochronometers, the records must be complete and the accumulation rates known.
The fossiliferous part of the geologic column includes perhaps 122,000 metres of sedimentary rock if maximum thicknesses are selected from throughout the world.
In addition to radioactive decay, many other processes have been investigated for their potential usefulness in absolute dating.
Practical experience indicates that the constant is almost totally dependent on temperature and that humidity is apparently of no significance.
During the late 1800s, attempts were made to estimate the time over which it formed by assuming an average rate of sedimentation.
Because there was great diversity among the rates assumed, the range of estimates was also large—from a high of 2.4 billion years to a low of 3 million years.
Most famous was the attempt to estimate the duration of Pleistocene interglacial intervals through depths of soil development.
In the American Midwest, thicknesses of gumbotil and carbonate-leached zones were measured in the glacial deposits (tills) laid down during each of the four glacial stages.
Although no hydration layer appears on artifacts of the more common flint and chalcedony, obsidian is sufficiently widespread that the method has broad application.