
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 geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochro ...
. The effort to define GSSPs is conducted by the
International Commission on Stratigraphy
The International Commission on Stratigraphy (ICS), sometimes unofficially referred to as the International Stratigraphic Commission, is a daughter or major subcommittee grade scientific organization that concerns itself with stratigraphy, strati ...
, a part of the
International Union of Geological Sciences
The International Union of Geological Sciences (IUGS) is an international non-governmental organization devoted to global cooperation in the field of geology. As of 2023, it represents more than 1 million geoscientists around the world.
About
Fo ...
. Most, but not all, GSSPs are based on
paleontological changes. Hence GSSPs are usually described in terms of transitions between different
faunal stages, though far more faunal stages have been described than GSSPs. The GSSP definition effort commenced in 1977. As of 2024, 79 of the 101 stages that need a GSSP have a ratified GSSP.
Rules
A geologic section has to fulfill a set of criteria to be adapted as a GSSP by the
ICS. The following list summarizes the criteria:
* A GSSP has to define the lower boundary of a geologic
stage.
* The lower boundary has to be defined using a primary marker (usually
first appearance datum of a fossil species).
** There should also be secondary markers (other fossils,
chemical,
geomagnetic reversal).
** The horizon in which the marker appears should have minerals that can be
radiometrically dated.
** The marker has to have regional and global correlation in outcrops of the same age.
** The marker should be independent of
facies.
* The outcrop has to have an adequate thickness.
* Sedimentation has to be continuous without any changes in facies.
* The outcrop should be unaffected by tectonic and sedimentary movements, and metamorphism.
* The outcrop has to be accessible to research and free to access.
** This includes that the outcrop has to be located where it can be visited quickly (International airport and good roads), has to be kept in good condition (ideally a national reserve), in accessible terrain, extensive enough to allow repeated sampling and open to researchers of all nationalities.
Agreed-upon Global Boundary Stratotype Section and Points
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). As such, GSSPs are also sometimes referred to as ''golden spikes''. The first stratigraphic boundary was defined in 1972 by identifying the
Silurian
The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...
-
Devonian
The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
boundary with a bronze plaque at a locality called
Klonk, northeast of the village of Suchomasty in the
Czech Republic
The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the south ...
.
Fortune Head GSSP
The
Precambrian-
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...
boundary GSSP at
Fortune Head,
Newfoundland
Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...
is a typical GSSP. It is accessible by paved road and is set aside as a
nature preserve. A continuous section is available from beds that are clearly Precambrian into beds that are clearly Cambrian. The boundary is set at the first appearance of a complex trace fossil ''
Treptichnus pedum'' that is found worldwide. The Fortune Head GSSP is unlikely to be washed away or built over. Nonetheless, ''Treptichnus pedum'' is less than ideal as a marker fossil as it is not found in every Cambrian sequence, and it is not assured that it is found at the same level in every exposure. In fact, further eroding its value as a boundary marker, it has since been identified in strata 4m ''below'' the GSSP.
However, no other fossil is known that would be preferable. There is no
radiometrically datable bed at the boundary at Fortune Head, but there is one slightly above the boundary in similar beds nearby.
These factors have led to suggestions that this GSSP is in need of reassigning.
Global Standard Stratigraphic Ages
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).
See also
*
Body plan
*
MN zonation
*
Fauna
Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...
*
Geologic time scale
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochro ...
**
New Zealand geologic time scale
*
North American land mammal age
*
Type locality
Notes
References
* Hedberg, H.D., (editor), ''International stratigraphic guide: A guide to stratigraphic classification, terminology, and procedure'', New York, John Wiley and Sons, 1976
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External links
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{{DEFAULTSORT:Global Boundary Stratotype Section And Point
Earth sciences
Geologic time scales of Earth
Historical geology
Paleogeography
Paleobiology
Units of time
Stratigraphy