Griesbachium
| series | step | Lower level | ≈ age ( mya ) |
|---|---|---|---|
| higher | higher | higher | younger |
| Lower Triassic | Olenekium | Space | 249.2-247.2 |
| Smithium | 251.2-249.2 | ||
| Indusium | Servantium | 251.6-251.2 | |
| Griesbachium | 251.9-251.6 | ||
| deeper | deeper | deeper | older |
Griesbachium (English Griesbachian, in German usage also just Griesbach or Griesbach level) is the lower lower level of the Indusium , the lowest level of the Triassic , in geological history . It follows the Changhsingium ( Perm ) and is replaced by the lower level of the Dienerium . The Griesbachium was originally proposed as a level by Edward Timothy ("Tim") Tozer in 1965 , but was later devalued to the informal lower level. The Griesbachium is still used in biostratigraphy.
Concept history
The name Griesbachium is derived from Griesbach Creek in the northwestern part of Axel Heiberg Island ( Qikiqtaaluk region , Nunavut , Canada ). This stream is again named after Carl Griesbach , a British paleontologist who worked in India for many years. The level and name were proposed by Edward Timothy ("Tim") Tozer in 1965.
Definition, absolute dating, correlation and subdivision
The lower limit of the Griesbachium is defined by the first appearance of the conodont species Hindeodus parvus . This is at the same time the lower limit of the Triassic system, the Lower Triassic series and the Indusium level. The GSSP (Global Boundary Stratotype Section and Point = "profile and point of a global limit Strato type ") for this limit is in Circle Changxing , in the province of Zhejiang in China . The upper limit and at the same time the lower limit of the dienerium is marked by the appearance of the family of the Gyronitidae ( Ammonites , Ammonoidea). The indusium (251.9 to 251.2) is a very short-lasting level with approx. 1.5 ma. Correspondingly, the Griesbachian, interpolated, would only have lasted about 600,000 years. According to Brühwiler et al. (2008), Griesbachium and Dienerium (= Indusium) together lasted about 1.4 ± 0.4 ma. The exact age of the Indusium / Olenekium border is also still uncertain (see Brack et al. (2005)).
The Griesbachium was originally proposed as a level by Edward Titmothy ("Tim") Tozer. Tozer had divided the Lower Triassic, the Scythian in the stratigraphy of the Tethyan Triassic, into a total of four levels, Griesbachian, Dienerium, Smithium and Spathium . Jean Guex 1978 merged the Dienerium and Smithium into a new level Nammalium. According to this structure, the Lower Triassic had three stages.
Since neither the four-level structure of the Lower Triassic by Tim Tozer nor the three-level structure of the Lower Triassic by Jean Guex was adopted in the international chronostratigraphic structure of the Triassic, but rather because the earlier Scythian was replaced by the two-level structure of the Indusium and Olenekian, Griesbachium and Dienerium became lower levels of the Indusium and the Smithium and Spathium "degraded" to lower stages of the Olenekian. They are considered to be informal sub-levels that are mainly used in biostratigraphy.
Despite the short time, the Griesbachium in the Tethyalen area can be biostratigraphically divided into three ammonite zones:
- Ophiceras tibeticum zone.
- Otoceras woodwardi zone
- Otoceras fissisellatum zone
Tozer originally identified four ammonite zones in the boreal area:
- Bukkenites strigatus
- Ophiceras commune
- Otoceras boreale
- Otoceras concavum
He combined the two lower ammonite zones into the Lower Griesbachian, the two upper ammonite zones into the Upper Griesbachian. In 1967 Tozer further divided the Griesbachian into two lower grades, the lower Gangetian (= Lower Griesbachian) and the upper Ellesmerian (Ellesmerian) (= Upper Griesbachian). However, today the Otoceras concavum zone and the lowest part of the Otoceras boreale zone are assigned to the Permian. The "lower Griesbachium sensu Tozer is thus reduced to the upper Oroceras boreale zone. The term" Gangetic lower stage "was coined by Libra and Diener in 1895 for the Otoceras woodwardi ammonite zone.
supporting documents
Individual evidence
- ↑ a b Frisch, Thomas (2011): Edward Timothy Tozer (1928-2010). Arctic, 64 (3): 388-389, Calgary. PDF
- ↑ Gradstein et al. (2004: p. 277)
- ↑ a b c Brühwiler, Thomas, Arnaud Brayard, Hugo Bucher, Kuang Guodun (2008): Griesbachian and Dienerian (Early Triassic) Ammonoid faunaus from northwestern Guangxi and southern Guizhou (South China). Palaeontology, 51 (5): 1151-1180, London doi : 10.1111 / j.1475-4983.2008.00796.x
- ↑ CL Griesbach - A Brief Biography ( Memento of the original from March 27, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (with picture)
- ↑ Brack, Peter, Hans Rieber, Alda Nicora and Roland Mundil (2005): The Global boundary Stratotype Section and Point (GSSP) of the Ladinian Stage (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale. Episodes, 28 (4): 233-244, Beijing ISSN 0705-3797 PDF ( Memento of the original from December 27, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. .
- ^ Guex, Jean (1978): Le Trias inférieur des Salt Ranges, Pakistan :problemèmes biochronologiques. Eclogae Geologicae Helvetiae, 71: 105-141, Basel. doi : 10.5169 / seals-164720
- ↑ TimeScale Creator 5.0 download page
literature
- Tozer, Edward Timothy (1965): Lower Triassic stages and ammonoid zones of Arctic Canada. Geological Survey of Canada Paper, 65-12: 1-14, Ottawa
- Tozer, Edward Timothy (1967): A standard for Triassic time. Geological Survey of Canada Bulletin, 156: 1-103, Ottawa.
- Gradstein, Felix, James Ogg & Alan Smith (2004): A Geologic Time Scale 2004. 589 pp. Cambridge University Press, Cambridge ISBN 0521781426