Which ratios are useful in determining the age of rocks or sediments?

The uranium-helium and uranium-lead ratios are significant in the determination of ages for rocks and sediments primarily because they both utilize radioactive decay processes to provide accurate age estimates.

Uranium-lead dating is one of the most reliable dating methods available. It relies on the decay of uranium isotopes into lead isotopes over time. By measuring the ratio of uranium to lead in a mineral, geologists can determine how long the decay has been occurring, which indicates the time since the rock or mineral crystallized.

Uranium-helium dating is utilized to date much younger minerals and can also provide insights relevant for geological time scales, particularly for the study of processes like thermal events and erosion.

Both methods are based on well-established principles of radiometric dating, making them robust in determining the geological timeline. They are particularly effective in dating igneous and metamorphic rocks, which can play a crucial role in understanding the history of Earth's crust.