Geochronology

Lore & Background

Geochronology encompasses both absolute dating, achieved through radioactive isotopes, and relative dating, provided by tools such as paleomagnetism and stable isotope ratios. Other techniques include electron spin resonance, fission-track dating, cosmogenic nuclide geochronology, luminescence dating, and amino acid dating.

Reader's Guide

Geochronology is fundamental to understanding Earth's history and the timing of geological and biological events. It works hand in hand with biostratigraphy, which assigns sedimentary rocks to geological periods based on fossil assemblages, though biostratigraphy does not directly provide absolute ages. The science uses incremental dating techniques such as dendrochronology, ice cores, lichenometry, and varves to construct year-by-year chronologies. Paleomagnetic dating and magnetostratigraphy determine age from magnetic polarity patterns, while chemostratigraphy uses global trends in isotope compositions like carbon-13 and strontium for correlation. Marker horizons, including tephrochronology, allow correlation of strata of the same age across different sites. Geochronological units (periods of time) are distinct from chronostratigraphic units (geological material); for example, one can visit an Upper Cretaceous Series deposit but not the Late Cretaceous Epoch.

Did You Know?

• Absolute geochronology can be accomplished through radioactive isotopes, while relative geochronology uses tools such as paleomagnetism and stable isotope ratios.
• Geochronological divisions from largest to smallest are: Eon, Era, Period, Epoch, Age, Chron.
• It is possible to visit an Upper Cretaceous Series deposit but not the Late Cretaceous Epoch, as the latter is a period of time.