A Global Boundary Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon stratigraphic section which serves as the reference section for a particular boundary on the geologic time scale. The effort to define GSSPs is conducted by the International Commission on Stratigraphy, a part of the International Union of Geological Sciences. 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 2004, 45 of the 96 GSSPs required have been approved.

Contents 1 An ideal GSSP 2 Agreed-upon GSSPs 3 GSSAs 4 See also 4.1 Related other topics 4.2 External links 5 Notes 5.1 References

[edit] An ideal GSSP

An ideal GSSP would:

• be accessible to research
• be extensive enough to ensure future access
• be easily related to other exposures worldwide
• contain a radiometrically datable bed at the boundary, and
• include well defined markers at the stage boundary that can be applied worldwide.

No GSSP is ideal.

[edit] Agreed-upon GSSPs

The Precambrian-Cambrian boundary GSSP at Fortune Head, Newfoundland 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 Trichophycus pedum that is found worldwide. The Fortune Head GSSP is unlikely to be washed away or built over. Nonetheless, Trichophycus 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!^[1] 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 lead some geologists to suggest that this GSSP is in need of re-assigning.

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 first stratigraphic boundary was defined in 1977 by identifying the Silurian-Devonian boundary with a bronze plaque at a locality called Klonk, northeast of the village of Suchomasty in the Czech Republic. GSSPs are also sometimes referred to as Golden Spikes.

[edit] GSSAs

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".

[edit] See also

e  h Units in geochronology and stratigraphy[2]
Segments of rock (strata) in chronostratigraphy	Periods of time in geochronology	Notes
Eonothem	Eon	4 total, half a billion years or more
Erathem	Era	12 total, several hundred million years
System	Period
Series	Epoch	tens of millions of years
Stage	Age	millions of years
Chronozone	Chron	smaller than an age/stage, not used by the ICS timescale

[edit] Related other topics

• Body form
• European Mammal Neogene
• Geologic time scale
  • New Zealand geologic time scale
• North American Land Mammal Age
• Fauna (animals)
• Type locality
• List of GSSPs

[edit] External links

• The Global Boundary Stratotype Section and Point (GSSP): overview
• Chart of The Global Boundary Stratotype Sections and Points (GSSP): chart
• Geotime chart displaying geologic time periods compared to the fossil record - Deals with chronology and classifications for laymen (not GSSPs)

[edit] Notes

[edit] References

• Hedberg, H.D., (editor), International stratigraphic guide: A guide to stratigraphic classification, terminology, and procedure, New York, John Wiley and Sons, 1976
• International Stratigraphic Chart from the International Commission on Stratigraphy
• USA National Park Service
• Washington State University
• Web Geological Time Machine
• Eon or Aeon, Math Words - An alphabetical index

v • d • e Chronology Major subjects Time · Astronomy · Geology · Paleontology · Archaeology · History Chronology Portal Eras and Epochs Calendar Eras: Ab urbe condita · Anno Domini / Common Era · Anno Mundi · Byzantine Era · Spanish era · Before Present · Hijri  · Egyptian · Sothic cycle · Hindu units of measurement · Hindu Yugas Regnal year: Canon of Kings · King lists · Limmu · Seleucid era Era name: Chinese · Japanese · Korean Calendars Pre-Julian Roman · Original Julian · Proleptic Julian · Revised Julian Gregorian · Proleptic Gregorian · Old Style and New Style Lunisolar · Solar · Lunar · Islamic · Chinese sexagenary cycle Astronomical year numbering · ISO week date Astronomic time and techniques Astronomical chronology · Cosmic Calendar · Ephemeris · Galactic year · Metonic cycle · Milankovitch cycles Geologic time scale and techniques Deep time · Geological history · Geological time units: Eons · Eras · Periods • Epoch • Age Dating Standards: GSSA • GSSP Chronostratigraphy · Geochronology · Isotope geochemistry · Law of superposition · Optical dating · Samarium-neodymium dating Archaeological techniques Dating methodology Absolute dating · Incremental dating · Archaeomagnetic dating · Dendrochronology · Glottochronology · Ice core · Lichenometry · Paleomagnetism · Radiocarbon dating · Radiometric dating · Tephrochronology · Thermoluminescence dating · Uranium-lead dating Relative dating · Seriation · Stratification Genetic techniques Amino acid dating · Molecular clock Related topics Chronicle · New Chronology · Periodization · Synchronoptic view · Timeline · Year zero · Circa · Floruit