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GSSP

From Simple English Wikipedia, the free encyclopedia
Many GSSPs are marked by golden spikes. This 'golden spike' marks the GSSP for the start of the Ediacaran.

A GSSP, more fully a Global Boundary Stratotype Section and Point, is an internationally agreed point which defines the start of a stage on the geologic time scale.

The work is done by the International Commission on Stratigraphy, a part of the International Union of Geological Sciences. As of 2012, 64 of the 101 stages that need a GSSP have been decided.[1]

Rules for GSSP

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A geologic section has to follow the rules to be adapted as a GSSP by the ICS. The list below are the rules:[2][3]

  • A GSSP has to decide the lower boundary (start of a geological period) of a geologic stage.
  • The lower boundary (start of a geological period) has to be decided using a primary (main) marker (usually first appearance datum of a fossil specie).
    • 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 acceptable thickness
  • Sedimentation has to be constant without any changes in facies
  • The outcrop should not be affected 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.

List

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This list shows some of the GSSPs.

Period Epoch Age (mya) Status GSSP location Defining markers Geographic Coordinates References
Phanerozoic
Cainozoic
Quaternary
Holocene 0.117
NGRIP2 ice core,

Greenland

 75°06′00″N 42°19′12″W / 75.1000°N 42.3200°W / 75.1000; -42.3200 [4]
Pleistocene 2.588
Monte San Nicola Section,

Sicily, Italy

 37°08′49″N 14°12′13″E / 37.1469°N 14.2035°E / 37.1469; 14.2035