Global Boundary Stratotype Section and Point

A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale.

The following list summarizes the criteria:[2][3] Once a GSSP boundary has been agreed upon, a 'golden spike' is driven into the geologic section to mark the precise boundary for future geologists (though in practice the 'spike' need neither be golden nor an actual spike).

The boundary is set at the first appearance of a complex trace fossil Treptichnus pedum that is found worldwide.

[citation needed] Because defining a GSSP depends on finding well-preserved geologic sections and identifying key events, this task becomes more difficult as one goes farther back in time.

Before 630 million years ago, boundaries on the geologic timescale are defined simply by reference to fixed dates, known as "Global Standard Stratigraphic Ages" (GSSAs).