GSSPs

Global Boundary Stratotype Section and Point (GSSP) is a globally recognized reference point in stratigraphy that marks the base of a stage on the geologic time scale. A GSSP is located at a precise bed or marker in a stratigraphic section and serves as the internationally accepted standard when naming a boundary between stages.

Development and governance: The concept originated with the International Commission on Stratigraphy (ICS) and its Subcommission on Stratigraphy. Proposals for new GSSPs are submitted by researchers and then undergo rigorous field studies, data compilation, and critical review. A GSSP must be well exposed, continuous, accessible, and representative of the marker horizon worldwide; it should be supported by multiple lines of evidence, including biostratigraphy, chemostratigraphy, magnetostratigraphy, and radiometric ages.

Implementation: Once approved, the GSSP becomes the reference point for that boundary in the International Chronostratigraphic Chart, and its status is published. The term GSSP is often referred to as a “golden spike”—a shorthand for the precise horizon that anchors a boundary.

Examples: The base of the Cambrian is defined at Fortune Head, Newfoundland, marked by the first appearance of the trace fossil Treptichnus pedum. The Permian–Triassic boundary is defined at Meishan, China, by the first appearance of conodont Hindeodus parvus.

Significance: GSSPs provide a fixed, globally recognizable framework for comparing rock records across continents and help standardize the geologic time scale. They are periodically reviewed as new data emerge, ensuring the time scale remains consistent with current evidence.