Type locality

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In geology and mineralogy, the type locality is the place (locality) from which the sample of a rock or mineral originates, on the basis of which it was first scientifically described. Usually this is an outcrop . Occasionally two or more type localities are given for minerals if samples from different locations were used to analyze the material. Often the respective rocks or minerals are named after the first place where they were found.

Analogously, also in the Paläontologie in the first description of a fossil species indicated a type locality. It is the location of the type specimen of this species. The corresponding expression in biology is type location (Terra typica) . Even with fossil species, the name often refers directly or indirectly to the type locality or the region in which the type locality is located.

The term is also extended to units of stratigraphy . For example, the GSSPs (Global Stratotype Section and Points) are type localities for chronostratigraphic units, and the definition of formations in lithostratigraphy is tied to a type locality. In the same sense, there are type localities for certain tectonic structures and for ore deposit types . In stratigraphy, one speaks informally of type regions in connection with entire landscapes that are geo (morpho) logically decisive and prototypically shaped by rocks of a certain sediment sequence .

The significance of the type locality in geology is comparable to the significance of the eponymous site in archeology.

Type localities and type profiles

Examples of rocks that are named after their type locality include the names Harzburgite and Lüneburgite , derived from the places Bad Harzburg and Lüneburg (Lower Saxony), the mineral Freibergite , after the place Freiberg , and the mineral Löllingite , which comes from the place Lölling (Carinthia) got its name, or rock formations like the Wettersteinkalk ( Wetterstein Mountains , Bavaria) and Dachsteinkalk ( Dachsteinmassiv , Austria).

A type locality can also be the location for several different rocks and minerals. The minerals Carlhintzeit (named after the mineralogist Carl Hintze ), hagendorfite (derived from the place name), phosphophyllite (characterized by composition and appearance), and strunzite (after the mineralogist Karl Hugo Strunz ) were found in Hagendorf for the first time . The small town of Moctezuma (in Sonora, Mexico) is not only Moctezumite but also type locality for twelve other minerals, including paratellurite , zemannite and spiroffite .

Examples of type localities of geological formations and structures are the Dinosaur Ridge in the US state of Colorado (west of Denver), this is where the type locality of the Morrison Formation lies . The caldera , the collapse structure of a volcanic crater, has the type locality of the Caldera de Taburiente on La Palma, one of the Canary Islands belonging to Spain. The Karst , the dry lime terrain, is derived from the Karst ridge (on the Adriatic Sea).

Type profile is the name given to the stratifications of lithostratigraphic units, as they exemplarily appear at the type locality. Usually the unit is then named after the locality, such as the Raibl layers after Raibl, today Cave del Predil , Friuli, or the Gosau group after the Gosau basin , where the type profiles of the most important subdivisions are also found. Entire chronostratigraphic time stages are then transferred according to type localities, such as the Lutetium (Lutet of the Eocene, from about 48 to 41 million years) to Lutetia ( Paris , introduced Lapparent 1883) or the new name Ionium for the Middle Pleistocene (the middle "Ice Age") ) after the Ionian Sea (upcoming nomenclature of the International Commission on Stratigraphy). The same applies to tectonic units, such as the Bajuvarikum of the Limestone Alps after the Bavarian Alps , where its incorporation is easy to read ( Tollman 1976)

Special type profiles / localities are the Global Stratotype Section and Points (GSSP) of the International Commission on Stratigraphy , which includes daily outcrops as well as drill cores . They serve to create a global correlation of geological strata sequences as seamlessly as possible, in order to be able to classify the numerous terms, often only introduced in small regions by authors since the late 18th century, into a global stratigraphic framework.

Web links

Individual evidence

  1. Type locality Moctezuma on mindat.org (English)