Radiometric dating sediments
Sediment cores from nine different lakes in the Tatra Mountains, collected as part of the EU funded AL: PE, MOLAR and EMERGE projects investigating natural environmental records stored in remote mountain lake sediment sequences, were dated radiometrically by 210Pb and 137Cs.
At five sites, Długi Staw Gąsienicowy and Zielony Staw Gąsienicowy on the Polish side of the Tatra Mountains and Starolesnianske pleso, Nižné Terianske pleso, and L’adové pleso on the Slovak side of the Tatra Mountains, the cores were sectioned at close intervals and analysed in detail to produce a high resolution chronology.
The same rock formation also contains a type of trilobite that was known to live 415 to 425 million years ago.
Since the rock formation contains both types of fossils the ago of the rock formation must be in the overlapping date range of 415 to 420 million years.
We define the rate of this radioactive decay in half-lives.
Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods.
Carbon-14, the radioactive isotope of carbon used in carbon dating has a half-life of 5730 years, so it decays too fast.
It can only be used to date fossils younger than about 75,000 years.
Then after another 5,000 years half of the remaining parent isotope will have decayed.
While people are most familiar with carbon dating, carbon dating is rarely applicable to fossils.