Global Boundary Stratotype Section and Point

A GSSP (Global Boundary Stratotype Section and Point, " profile and a global point boundary - layer type " ) is a geological outcrop, which serves as a reference in establishing a chronostratigraphic unit ( type locality ). The geological profile of the pulping process is studied and described geologically to the last detail. Also the location of the reference point in the profile is well defined. There are now more than a hundred GSSPs (see list of GSSPs ).

The determination of the globally applicable GSSPs done by the International Commission on Stratigraphy (ICS ), a subsidiary organization of the International Union of Geological Sciences ( IUGS ​​). The case applicable GSSP method is also defined exactly. It was documented in 1976 in the first issue of the International Stratigraphic Guide and first used in 1977 in establishing the boundary between the Silurian and Devonian systems in La Serre in the department of Aveyron ( south of France ).

Method

Methodology

The GSSP method defines a chronostratigraphic unit by the type and the " base point ". The type consists of a reference profile in the vertical rock sequence a particular position is determined to be " low end " of the unit. This position is in line with the image of a large, marked nail called the Golden Spike. The unit includes all the rocks that were formed over time between this boundary and the boundary of the following unit. A GSSP is defined by international bodies such as the International Commission of Stratigraphy after an intensive selection process, and is accepted in the sense of unique content designation of the chronostratigraphic units of virtually all geoscientists.

Benefits

Compared to other methods (eg the definition of means of biostratigraphy or by a geochronologisches absolute age), this type of definition of a chronostratigraphic unit some advantages: it is objectively in the way that it points to an immutable and objective quality of the reference profile. Subjectively remains alone transfer to reserves away from the reference profile. With the progress of knowledge in independent auxiliary disciplines, such as the Eventstratigraphie, a further refinement of the identification of this boundary in other outcrops is possible. Nor can this today, do not use known, future procedures.

The GSSP - defined procedure directly neither an absolute age nor an absolute time interval. A direct absolute temporal definition of a rock unit is also not useful because the methods of relative dating currently in force on the radiometric method of age determination in many cases have a higher resolution. However, since the corresponding geochronological units depend at least in the Phanerozoic of the definitions of chronostratigraphic units, change and shift the absolute time values ​​with the application of improved dating methods.

Requirements

Although such a GSSP can be defined in any profile, in principle, at any position, met a good, certain majority in the selection process efficient GSSP requirements. he

  • Is in the vicinity of golden spikes as free as possible of Sedimentationslücken
  • Is located in a position that is correlated as possible with an easily recognizable and most trackable markers
  • Provides a wealth of useful information for the correlation
  • Is available and accessible for scientific investigations
  • Is under a certain amount of protection and is thereby secured in the long term
  • Possible forms from a historically established limit position
Ediacaran List of Global Boundary Stratotype Sections and Points Radiometry
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