Stability and precision in chronostratigraphic definition: The Global Boundary Stratotype Section and Point (GSSP) is the solution

The concept of the Global Boundary Stratotype Section and Point (GSSP) to define the bases of chronostratigraphic units, indicated by a spike in rock, has endured for over half a century. Each boundary is defined by a spike in a rock succession, coincident with available biological and or other markers and represents a unique point in time to serve as the standard (yardstick) against which other successions can be correlated. The GSSPs are geological standards, referred to as stratotypes and are key reference points in time. The methodology has brought precision and stability to the definition of geological time, providing a global language for Earth science and Earth scientists. It is the largest cooperative venture in the history of the Earth sciences. In recent years, some challenges to this practice have been voiced questioning the validity of the GSSP concept. It is thus opportune to address misconceptions and misunderstandings and clearly reiterate the necessity of this approach and its success.