Series (stratigraphy)

A series (English series) is in Earth's history, a time unit of chronostratigraphy. It is similar to the geochronological division of geological epoch of the unit. The terms are often used as synonyms not entirely correct, since they are each defined somewhat differently. The unit of time " series " or " era " usually includes periods of several million to several tens of millions of years.

Definition

The series is the next higher level to the chronostratigraphic unit that is the basic unit in the Chronostratigraphy. The imaginary isochronous boundaries of chronostratigraphic unit " series" are like the other units of chronostratigraphy relatively dated, that is bound in the context of other chronostratigraphic series and systems, and are concrete to rock body. For this purpose, a GSSP must be set for all chronostratigraphic boundaries. The absolute age and the amount of time a chronostratigraphic series is not included in this definition. The time period that corresponds to the geochronology of a series is called epoch. The absolute age of the grounds specified in the limits can still change due to the methodological inaccuracies of age determination methods. The chronostratigraphic series internationally used are defined by the ICS ( International Commission on Stratigraphy ) and ratified (see Geologic time scale).

Structure

A series can represent in exceptional cases only a single stage (eg, the Pridolium stage and series ), but mostly it comprises several stages. The hierarchical unit of the series is in the Chronostratigraphy the system. In the era of geochronology is a subunit of the period and is itself divided into several age.

Naming

The name of the series will be either by enclosing the attributes "Lower ", "Middle " or "Upper " to the system name or by enclosing the prefix " sub " - refers to the system name - "medium" - and " top ". There are some cases, however, used their own name (eg, Llandovery, Wenlock and Lodlow in the Silurian ). The latter were originally defined as levels and raised until later in the hierarchical rank of a series. In the era name of the geochronology are usually by the period name with the addition of the adjectives " early" and "late" capabilities (eg, Early Cretaceous, etc.). The term " series" in geology is problematic, because as a "Series" also lithostratigraphic units or units in the hierarchical rank of a stage is called (eg in the work of Chicha et al., 1967) in older parlance. Erroneously, the term is also sometimes combined with the names of systems (for example, "Chalk Series"). Such names and combinations should be avoided in the future. In the older literature, there is also the term used to denote a division series. This concept also should not be used any more.