Uth

UTh is an abbreviation commonly used to refer to uranium-thorium dating, a radiometric dating method used to determine the age of calcium carbonate materials such as stalagmites, corals, and other carbonate sediments. The method relies on the radioactive decay of uranium isotopes within the carbonate.

Principle and procedure: When carbonate forms, thorium is chemically excluded, while uranium is incorporated. Over time, 238U decays to 234U and then to 230Th. The amount of 230Th relative to 238U increases as time passes, allowing the age to be calculated from measured isotope ratios. Mass spectrometry or similar techniques quantify 238U, 234U, and 230Th (and often 232Th as a proxy for detrital Th). Accurate ages require correction for any initial 230Th and for detrital thorium contamination, as well as careful consideration of the sample’s geological history.

Range and applications: U-Th dating is particularly suited for carbonate materials and is effective from several hundred years up to roughly 500,000 years, depending on the system and sample quality. It is widely used in paleoclimate research to date speleothems (cave formations), reef and coastal corals, and other carbonate records, contributing to reconstructions of past climate, rainfall, and sea-level change.

Limitations: Potential open-system behavior, detrital thorium contamination, and assumptions about initial conditions can affect accuracy. The method requires well-preserved carbonate with sufficient uranium and low initial thorium, as well as high-precision isotope measurements.

Other uses: In nuclear science contexts, the terms U and Th may also appear in discussions of uranium-thorium fuel cycles, where thorium-232 is used to breed uranium-233 for potential reactor fuel, though this usage is unrelated to dating.