Radioactive atoms are inherently unstable; over time, radioactive "parent atoms" decay into stable "daughter atoms." When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.
From: Wikimedia Commons We can indirectly date glacial sediments by looking at the organic materials above and below glacial sediments. Marine geological constraints for the grounding-line position of the Antarctic Ice Sheet on the southern Weddell Sea shelf at the Last Glacial Maximum.
Uranium-lead dating is one of the most complicated of all dating techniques.
This is in part because uranium and lead are not retained in rocks as easily as some others, and in part because the parent isotopes and daughter products are not even directly related.
Radiocarbon dating provides the age of organic remains that overly glacial sediments.
It was one of the earliest techniques to be developed, during the 1940s.