Global Boundary Stratotype Section and Point
A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a
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:[2][3]
- 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). The first stratigraphic boundary was defined in 1972 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.
Fortune Head GSSP
The
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).
As of March 2024, there are two "formalized" GSSAs, one for the base of the Hadean (ratified October 2022), and the other for the base of the Archean and Eoarchean (ratified in mid-late 2023).[6] These are defined based on dates obtained from physical samples, and can have associated physical stratotypes. This is in contrast to non-formalized GSSAs, which are arbitrary age estimates with no imprecision.
See also
Segments of rock (strata) in chronostratigraphy | Time spans in geochronology | Notes to geochronological units |
---|---|---|
Eonothem | Eon | 4 total, half a billion years or more |
Erathem | Era | 10 defined, several hundred million years |
System | Period | 22 defined, tens to ~one hundred million years |
Series | Epoch | 34 defined, tens of millions of years |
Stage | Age | 99 defined, millions of years |
Chronozone | Chron |
subdivision of an age, not used by the ICS timescale |
- Body plan
- MN zonation
- Fauna
- Geologic time scale
- List of Global Boundary Stratotype Sections and Points
- North American land mammal age
- Type locality
Notes
- ^ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. Retrieved 2024-03-17.
- (PDF) from the original on 2015-03-18.
- ^ "GSSP Rules". Geologic Timescale Foundation. Archived from the original on 2023-01-24. Retrieved 2024-03-17.
- ^ "GSSP table with pages on each ratified GSSP". ICS Subcommission for Stratigraphic Information. Archived from the original on 2017-01-02. Retrieved 2024-03-17.
- (PDF) from the original on 2017-08-11.
- ^ "Global Boundary Stratotype Section and Points". stratigraphy.org. International Commission on Stratigraphy. Archived from the original on 2024-01-11. Retrieved 2024-03-17.
- ^ Cohen, K.M.; Finney, S.; Gibbard, P.L. (2015), International Chronostratigraphic Chart (PDF), International Commission on Stratigraphy.
References
- Hedberg, H.D., (editor), International stratigraphic guide: A guide to stratigraphic classification, terminology, and procedure, New York, John Wiley and Sons, 1976[ISBN missing]
- "International Stratigraphic Chart". International Commission on Stratigraphy. Archived from the original on 2019-04-03.
- "GSSP table with pages on each ratified GSSP". ICS Subcommission for Stratigraphic Information. Archived from the original on 2017-01-02.
- "What is Geologic Time?". USA National Park Service. Archived from the original on 2008-09-23.
- "Earth Science: Geologic Age". Washington State University. Archived from the original on 2011-07-26.
- "Web Geological Time Machine". ucmp.berkeley.edu. Archived from the original on 2021-04-27.
- "Aeon or Eon". pballew.net. Archived from the original on 2010-06-18., "Math Words – An alphabetical index". pballew.net. Archived from the original on 2010-07-24.
External links
- "The Global Boundary Stratotype Section and Point (GSSP): overview". stratigraphy.org. Archived from the original on 2009-01-13.
- "Chart of The Global Boundary Stratotype Sections and Points (GSSP): chart". stratigraphy.science.purdue.edu. Archived from the original on 2022-06-30.
- "GSSP Table - All Periods". timescalefoundation.org. Archived from the original on 2023-11-30.
- "GSSPs and Continental drift 3D views". ghkclass.net. Archived from the original on 2023-12-08.
- "Geotime chart displaying geologic time periods compared to the fossil record – Deals with chronology and classifications for laymen (not GSSPs)". rocksandminerals.com. Archived from the original on 2023-12-07.