Dating using Thorium230

Dating techniques using thorium are employed on oceanic sediments that are older than the range that radiocarbon techniques can detect. Uranium that is present in seawater eventually decays to thorium-230 (called ionium), is precipitated into the ocean floor sediments, and is stored. Thorium-230, which is part of the uranium-238 decay series, has a half-life of 80,000 years. Protactinium-231, which is derived from uranium-235, has a half-life of 34,400 years. Both can be used for age calculations. This method has been used on deep-sea sediments formed during the past 300,000 years.

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