A radiometric dating technique based on the rate at which uranium-238 and thorium-230 fission. This method has been used to date organic marine sediments, bone, wood, coral, stone, and soil from deep water, cave, or land fall areas. The time range that has been dated with this method so far is less than 300,000 to about 1,000,000 years ago. The half-life of U-238 is 4. 468 billion years and the half-life of Th-230 is 75,380 years. This is one of several uranium series dating methods.