Geochronology

• Geochronology


  • Geochronology measures the age of Earth materials, as well as provides a temporal framework for the landscapes of Earth’s history
  • Geochronology helps us understand the rate of landscape formations, and timeframes for when they eroded, or when sediments were deposited
  • It is important as it helps us understand the complex nature of temporal scales of Earth’s landscapes and systems
  • Relative and absolute dating methods can be used to provide age estimates
• Radiometric Dating


  • Uses absolute dating methods through chemical processes. This includes: radio carbon dating, K/Ar dating and uranium dating
  • These processes use the rate of known half-lives between parent and daughter isotopes to determine the age of materials
  • K/Ar used in volcanic dating
  • U/Th dating used in karst landscapes
  • Radiocarbon dating is used in dating organic materials such as shells or other in situ material
• Radiometric Dating- Weathering


  • We can also date weathering, as weathering leads to the production of clays and iron oxyhydroxides
  • These minerals contain U and Th, as the atoms experience alpha decay, He accumulates in the minerals
  • So, we can use U-Th/He dating to calculate the weathering age of an outcrop
• Surface Exposure Dating


  • Primarily used on glaciated striated surfaces or desert pavements, measures how long the surface has been exposed to cosmic rays
  • Secondary cosmic rays that travel through the atmosphere interact with the exposed rock surface and produce nuclear reactions in atoms near the surface
  • N= P x t (N- nuclide concentration, P- production rate, t- time)
  • Known rates of exposure to secondary cosmic ray, contribute to the knowledge of the rates of formation of the landscape
  • This method only works well on surfaces that have not been extensively weathered