protactinium-ionium age method

protactinium-ionium age method

[¦prōd‚ak′tin·ē·əm ī′ō·nē·əm ′āj ‚meth·əd]
(geology)
A method of calculating the ages of deep-sea sediments formed during the last 150,000 years from measurements of the ratio of protactinium-231 to ionium (thorium-230), based on the gradual change of this ratio over time because of the difference in half-lives.