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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 A stratigraphic section is a sequence of layers of rocks in the order they were deposited. It is based on the principle of original horizontality, which states that layers of sediment are originally deposited horizontally under the action of ...
which defines the lower boundary of a
stage Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...
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 Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
changes. Hence GSSPs are usually described in terms of transitions between different
faunal stage In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by conven ...
s, 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 Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...
. * The lower boundary has to be defined using a primary marker (usually
first appearance datum First appearance datum (FAD) is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. FADs are determined by identifying the geologically oldest fossil discovered, to date, of a partic ...
of a fossil species). ** There should also be secondary markers (other fossils,
chemical A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...
,
geomagnetic reversal A geomagnetic reversal is a change in the Earth's Dipole magnet, dipole magnetic field such that the positions of magnetic north and magnetic south are interchanged (not to be confused with North Pole, geographic north and South Pole, geograp ...
). ** 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 In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...
. * 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 Klonk is a national nature monument in the Bohemian Karst Protected Landscape Area in the Czech Republic. It lies in the northern part of the municipality of Suchomasty, approximately south of Beroun. It is globally recognized as a geologica ...
, 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 The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...
-
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 Fortune Head is a headland located about from the town of Fortune on the Burin Peninsula, southeastern Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises t ...
,
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 nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, funga, or features of geolog ...
. 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 ''Treptichnus'' (formerly named ''Phycodes'', ''Manykodes'' by Jerzy Dzik, J. Dzik, and also known as ''Trichophycus''See e.gfossiilid.info: paleodiversity in Baltoscandia: Trichophycus pedum/ref>) is the preserved burrow of an animal. As such, ...
'' 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 A body plan, (), or ground plan is a set of morphology (biology), morphological phenotypic trait, features common to many members of a phylum of animals. The vertebrates share one body plan, while invertebrates have many. This term, usually app ...
*
MN zonation The Mammal Neogene zones or MN zones are system of biostratigraphic zones in the stratigraphic record used to correlate mammal-bearing fossil localities of the Neogene period of Europe. It consists of seventeen consecutive zones (numbered MN 1 thr ...
*
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 While also using the international geologic time scale, many nations–especially those with isolated and therefore non-standard prehistories–use their own systems of dividing geologic time into epochs and faunal stages. In New Zealand, the ...
*
North American land mammal age The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when ref ...
* 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 * * * * * * ,


External links

* * * * * {{DEFAULTSORT:Global Boundary Stratotype Section And Point Earth sciences Geologic time scales of Earth Historical geology Paleogeography Paleobiology Units of time Stratigraphy