Argon argon dating
– Scientists at the University of California, Berkeley, and the Berkeley Geochronology Center have pinpointed the date of the dinosaurs' extinction more precisely than ever thanks to refinements to a common technique for dating rocks and fossils.
The argon-argon dating method has been widely used to determine the age of rocks, whether they're thousands or billions of years old.
Because Earth's orbit, and thus the relative ages of the sediment layers, can be precisely calculated, dating of the sediments by the argon-argon method provided a much-needed recalibration of the method and made it possible to pinpoint the Cretaceous/Tertiary boundary at 65.95 million years ago.The collaboration brought together all the appropriate expertise to bring this approach to fruition, he said."The problem with astronomical dating of much older sediments, even when they contain clear records of astronomical cycles, is that you're talking about a pattern that is not anchored anywhere," Renne said."You see a bunch of repetitions of features in sediments, but you don't know where to start counting."Argon-argon dating of volcanic ash, or tephra, in these sediments provided that anchor, he said, synchronizing the methods and making each one more precise.The method relies on satisfying some important assumptions: Given careful work in the field and in the lab, these assumptions can be met.The rock sample to be dated must be chosen very carefully.
Renne and his colleagues in Berkeley and in the Netherlands now have lowered this uncertainty to 0.25 percent and brought it into agreement with other isotopic methods of dating rocks, such as uranium/lead dating.