Non-destructive gamma spectrometric U-series dating. This means that uranium is present in water which seeps into limestone caves but it's non-soluble daughter products are not. This excess is transferred to organisms such as mollusks or corals, and is the basis of Uranium series have been used to date uranium-rich rocks, deep-sea sediments, shells, bones, and teeth, and to calculate the ages of ancient lake beds. Protactinium begins to accumulate via the decay of U after the organism dies. In the case of a daughter excess, a larger amount of the daughter is initially deposited than the parent.