Luis and Walter Alvarez discovered the rare radioactive element Iridium and other elements in an obvious clay layer at the K-T (Cretaceous/Terseary) Boundary in Gubbio, Italy 1981 over the last dinosaur fossils. Iridium in abundance is found only in meteorites. Luis suggested the use of radioactive Beryllium 10 to help date the layer.
Beryllium-10 used to date ice cores - Wikipedia https://en.wikipedia.org/wiki/Beryllium-10
Beryllium-10 (10Be) is a radioactive isotope of beryllium. It is formed mainly by the cosmic rays on exposed surfaces. The oldest quartz it can date is 800 thousand years. Besides Carbon 14, Beryllium-10 is another cosmogenic (formed by cosmic rays from space) isotope that is frequently utilized for recent Pleistocene dating due to their short decay rates. Be 10 has become extremely popular within the last decade for dating quartz-rich rocks such as granite and granodiorite. 10Be dating may be applied to boulders, glacial loess or other sediments that were exposed at the surface.
When this boundary was first discovered they needed to date this surface. Louis Alvarez physicist discussed with Walter Alvarez his son a professor of earth science, and Luis suggested using beryllium-10, which is laid down at a constant rate in sedimentary rocks and then radioactively decays. Perhaps beryllium could serve as a timer.
Richard Muller, another physicist was asked to join their team and measure the amount of Be10 in this Cretaceous boundary clay.
http://undsci.berkeley.edu/article/0_0_0/alvarez_03Luis Alvarez was awarded the Nobel Prize for physics in 1968. ... question with his father, the physicist Luis Alvarez, who suggested using beryllium-10...
“However, before they could take the beryllium measurements, they learned that the published decay rate for the isotope was wrong. Calculations based on the new numbers revealed that the planned analysis would not work. For the amounts of beryllium that they could detect, the timer in the 65 million year old clay layer would have already run out — all of the beryllium would have decayed away."
They learned this from evolutionists that Be10 would not last long enough to date a layer 65 million years old. It can only date specimens no older than 800 thousand years. So this method has not been used.
This was a mistake, because they would have found that the clay DOES contain Be10 because dinosaurs were buried no more than 4500 years ago. This would confirm the dates gotten from dinosaur bones from Carbon 14 and soft dinosaur tissue which also do not last for millions of years.
See details in my books: