Yokoyama Y. All we care about is that the measurements ranged from years to 40, years, which hardly inspires confidence in the method. There is no reason to believe that the various isotopes of uranium and thorium were initially distributed any more evenly than gold was. Whatever process that created the Earth did not distribute all the elements evenly. Uranium series and ESR dates. All we need to know is, surprisingly, found in a table on the New York State Department of Health website. A series, all seawater and constraints imposed by the 14th 15th.
Not much, as we will see, later.
Edwards, L. Uranium series dating of impure carbonates: In other words, after 10 million years essentially all of the original U should be gone, and all that should be left is the U that was created by decay of U, which should be in equilibrium by now. The simplest shape is a straight line, like the one below. The Th decays to Pa in a matter of months, which almost instantly decays to U; so it is pointless to try to measure the thorium or protactinium. DD dating is useful on chemically precipitated CaCO 3 and some biogenic carbonates.