isotope stratigraphy

Isotope stratigraphy is a method used in geology to correlate rock layers, particularly those of younger ages like those from the Cenozoic Era. It analyzes variations in isotopes, such as oxygen, carbon, and strontium, within layered rocks like limestone.1

These isotopic variations can indicate changes in climate and long-term erosion patterns. For example, high ratios of oxygen isotopes (¹⁸O to ¹⁶O) or carbon isotopes (¹³C to ¹⁴C) can suggest colder periods with lower sea levels, while low ratios indicate warmer periods with higher sea levels. Similarly, high strontium isotope ratios (⁸⁷Sr to ⁸⁶Sr) often point to increased erosion and the transfer of radiogenic strontium from continents to oceans during warmer climates.1

This method assumes that marine invertebrate shells and carbonate sediments can record isotopic changes in seawater, providing a way to date and correlate rock strata globally. Isotope stratigraphy complements traditional methods like fossil dating and radiometric dating.1234