method of age determination that makes use of the radioactive decay of uranium-238 to uranium-234; the method can be used for dating of sediments from either a marine or a playa lake environment. Because this method is useful for the period of time from about 100,000 years to 1,200,000 years before the present, it helps in bridging the gap between the carbon-14 dating method and the potassium-argon dating method.