Global Boundary Stratotype Section and Point
A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a
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). 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
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".
|Segments of rock (strata) in chronostratigraphy||Time spans in geochronology||Notes to|
|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|
|subdivision of an age, not used by the ICS timescale|
- Body plan
- MN zonation
- Geologic time scale
- List of Global Boundary Stratotype Sections and Points
- North American land mammal age
- Type locality
- ^ "International Chronostratigraphic Chart 2022". International Commission on Stratigraphy. Retrieved 16 January 2023.
- (PDF) from the original on 2015-03-18.
- ^ "GSSP Rules". Geologic Timescale Foundation. Retrieved 28 November 2012.
- ^ "GSSP Table - All Periods". Geologic Timescale Foundation. Retrieved 29 November 2012.
- S2CID 131211543.
- ^ Cohen, K.M.; Finney, S.; Gibbard, P.L. (2015), International Chronostratigraphic Chart (PDF), International Commission on Stratigraphy.
- 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 from the International Commission on Stratigraphy
- GSSP table with pages on each ratified GSSP from the ICS Subcommission for Stratigraphic Information
- USA National Park Service
- Washington State University Archived 2011-07-26 at the Wayback Machine
- Web Geological Time Machine
- Eon or Aeon, Math Words – An alphabetical index
- The Global Boundary Stratotype Section and Point (GSSP): overview
- Chart of The Global Boundary Stratotype Sections and Points (GSSP): chart
- Table of Global Boundary Stratotype Sections and Points (GSSPs) with links to summary pages for each one: chart
- GSSPs and Continental drift 3D views
- Geotime chart displaying geologic time periods compared to the fossil record – Deals with chronology and classifications for laymen (not GSSPs)