World Library  
Flag as Inappropriate
Email this Article

Global Boundary Stratotype Section and Point

Article Id: WHEBN0000012451
Reproduction Date:

Title: Global Boundary Stratotype Section and Point  
Author: World Heritage Encyclopedia
Language: English
Subject: Ediacaran, Stage (stratigraphy), Pleistocene, Chronicle, Paleobiology
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Global Boundary Stratotype Section and Point

The 'golden spike' (bronze disk in the lower section of the image) or 'type section' of the Global Boundary Stratotype Section and Point (GSSP) for the base of Ediacaran period.
The 'golden spike' marking the Ediacaran GSSP

A Global Boundary Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage 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 2012, 64 of the 101 stages that need a GSSP have been formally defined.[1]

Rules for GSSP

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 GSSPs

Global Boundary Stratotype Section and Point is located in Earth
World map of all ratified GSSPs.[4]

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 Treptichnus pedum 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![5] 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 some geologists to suggest that this GSSP is in need of reassigning.

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.

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".

See also

Units in geochronology and stratigraphy[6]
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
14 total, several hundred million years
System
Period
Series
Epoch
tens of millions of years
Stage
Age
millions of years
Chronozone
Chron
subdivision of an age, not used by the ICS timescale

Related other topics

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
  • GSSP table with pages on each ratified GSSP from the ICS Subcommission for Stratigraphic Information
  • USA National Park Service
  • Washington State University
  • Web Geological Time Machine
  • Eon or Aeon, Math Words - An alphabetical index

Notes

  1. ^ "International Chronostratigraphic Chart 2012". ICS. Retrieved 28 November 2012. 
  2. ^
  3. ^ "GSSP Rules". Geologic Timescale Foundation. Retrieved 28 November 2012. 
  4. ^ "GSSP Table - All Periods". Geologic Timescale Foundation. Retrieved 29 November 2012. 
  5. ^ Gehling, J.; Jensen, S. R.; Droser, M.; Myrow, P.; Narbonne, G. (March 2001). "Burrowing below the basal Cambrian GSSP, Fortune Head, Newfoundland". Geological Magazine 138 (2): 213–218.  
  6. ^ Cohen, K.M., Finney, S., Gibbard, P.L. (2013), International Chronostratigraphic Chart, International Commission on Stratigraphy .

External links

  • 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
  • Geotime chart displaying geologic time periods compared to the fossil record - Deals with chronology and classifications for laymen (not GSSPs)
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.