Methods for volcanic dating
New dating methods are invented all the time, however, most have practical limitations.
Geologic research and mapping requires the determinations of the ages and composition of rocks.
Tephrochronology is the study of volcanic ash deposits.
Volcanic ash layers often have unique chemical and physical characteristics that can be used for correlation.
Paleontologists frequently work in conjunction with other scientists utilizing any number of other geochronology methods.
Like fossils, the chemical and physical characteristics of rocks, minerals, and organic materials can be used for correlation.
Geochronology is the science of dating and determining the time sequence of events in the history of the Earth.
This web page provides an overview of selected geochronology methods used by USGS scientists.
For more information, contact Andrei Sarna-Wojcicki. Strontium Geochronology - With modern isotope separation equipment, the content of selected elemental isotopes can now be measured in concentrations to parts-per-million to parts-per-billion and beyond.
A relative age of the original shell can be established by comparing the strontium isotope ratio of the shell material to published data for the time periods where this method is usable.
The method is most effective when used in conjunction with other dating methods. Stable Isotope Records - Stable isotope data derived from mineral and biological materials can provide a variety of insights into environmental conditions (past and present), and can be used in geochronology and correlation.
Oxygen isotopes (-O) are widely used in correlation of Quaternary marine sediments.
Oxygen isotope concentrations in mollusk shell and calcareous algal material normalize with seawater while the organisms are alive.