boundary stratotype

A boundary stratotype, also known as a Global Boundary Stratotype Section and Point (GSSP), is a specific point in the rock record used to define the boundary between geological time units. These stratotypes serve as reference points for global correlation, helping geologists pinpoint precise moments in Earth's history.12

The International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS) are responsible for establishing these boundary stratotypes. For instance, the boundary between the Tertiary and Quaternary periods (now redefined as the Neogene and Quaternary periods) has been stratotypified in Sicily, Italy, dated to approximately 2.6 million years ago. Other significant boundary stratotypes include the Cretaceous-Tertiary (K-T) boundary, estimated at 66 million years ago, and the Paleocene-Eocene boundary, dated to 56 million years ago. These markers are crucial for understanding the sequence and timing of geological events and the evolution of life on Earth.123