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How do Global Boundary Stratotype Sections and Points help geologists compare rock layers worldwide?

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Cenozoic migration routes — Cenozoic Era Principal Cenozoic faunal migration routes and barriers.

Global Boundary Stratotype Sections and Points (GSSPs), often referred to as a "golden spike," are essential tools for geologists to standardize the geologic time scale worldwide.12

By designating a specific, observable point in a rock sequence as the official lower limit of a chronostratigraphic unit, geologists create a fixed reference point where time and rock coincide. These stratotypes serve as the "linchpins" of global correlation, providing a definitive standard that allows researchers to compare rock layers across different regions.1

Rather than relying solely on variable local descriptions, geologists use these internationally ratified markers to establish a consistent framework for identifying the boundaries between geologic periods and epochs. This ensures that when scientists discuss a specific interval of time, they are referencing the same physical evidence in the rock record, regardless of where they are working globally.12