CoachA stratotype is the designated section of rock that serves as the standard of reference for a unit or a boundary. A unit stratotype is the type section of a whole unit; a boundary stratotype is the section that contains the specific point defining a boundary between two units. A global boundary stratotype section and point (GSSP) is the boundary stratotype of a unit of the international chronostratigraphic scale: a single point in a single section, chosen by international agreement, which defines the base of a stage and of every larger unit that begins with it.
| base of | age () | section | marker of the point | ratified |
|---|---|---|---|---|
| Fortunian (Cambrian) | 538.8 | Fortune Head, Newfoundland, Canada | first appearance of the trace fossil Trichophycus pedum | 1992 |
| Lochkovian (Devonian) | 419.62 | Klonk, near Prague, Czech Republic | first appearance of the graptolite Monograptus uniformis | 1972 |
| Induan (Triassic) | 251.902 | Meishan, Zhejiang, China | first appearance of the conodont Hindeodus parvus, base of Bed 27c | 2001 |
| Danian (Paleogene) | 66.00 | Oued Djerfane, El Kef, Tunisia | base of a dark boundary clay; iridium anomaly | 1991 |
| Selandian | 61.66 | Zumaia, Spain | base of red marls; second radiation of a nannofossil group | 2008 |
| Ypresian (Eocene) | 56.00 | Dababiya, near Luxor, Egypt | base of a carbon-isotope excursion | 2003 |
| Chibanian | 0.774 | Chiba, Japan | base of a tephra, just below a magnetic reversal | 2020 |
| Meghalayan | 0.0042 | Mawmluh Cave, Meghalaya, India | a level deep in a speleothem | 2018 |