Smithium

from Wikipedia, the free encyclopedia
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

Smithium (English Smithian) is a (short) time interval in the history of the earth . It is the upper lower stage of the Olenekian , the second stage of the Triassic . It follows the Dienerium , the upper lower level of the Indusium, and is replaced by the Spathium .

Concept history

The Smithium is named after Smith Creek in the northwestern part of Ellesmere Island . This stream is again named after James Perrin Smith , an American paleontologist. The level and name were suggested by Tim Tozer in 1965. Since Dienerium and Smithium are often difficult to separate biostratigraphically in areas outside of Arctic Canada, Jean Guex proposed in 1978 to combine the two stages and coined the new stage name Nammalium .

Definition, absolute dating, correlation and subdivision

The basis of the Smithium was originally defined by Tozer with the onset of the ammonite species Euflemingites romunderi . Later, in a revised definition, the Hedenstroemia-hedenstroemi zone was inserted between the uppermost ammonite zone of the Dienerium and the Smithium ; d. H. the smithium now begins at the base of this zone. The conodont species Neospathodus waageni also begins at this border. The upper limit and at the same time the lower limit of the space below it is characterized by the onset of the ammonite genera Tirolites , Columbites , Subcolumbites , Prohungarites and Keyserlingites . The first onset of the ammonite species Subolenekites pilaticus was formally defined as the lower limit. However, an ammonite zone seems to be missing in the type profile. In the Tethys, the ammonite species Tirolites cassianus begins at this border .

The time interval of the Smithium is geochronologically dated to 251.2 to 249.2 million years ago. For the alternative dating of the Lower Triassic see (Brack et al. 2005).

The Smithium is now correlated with the Lower Olenekian. Since the border was a bit insecure for a long time, Jean Guex (1978) proposed that Dienerium and Smithium be combined into a lower level. He called this lower level Nammalium . This proposal initially seemed to prevail, but was later abandoned in favor of the two-tier structure of the Lower Triassic. The same limits are assumed for the Ayaxium lower level (Ayaxian); this lower level was suggested by Zakharov (1994). However, the ayaxium did not find acceptance.

The Smithium is divided into three ammonite zones:

The Smithium is not an "official" one. H. Lower level recognized and defined by the International Commission on Stratigraphy (ICS), but only an "informal" time interval. Even so, it is used in recent work on the Lower Triassic.

supporting documents

Individual evidence

  1. ^ A b Guex, Jean (1978): Le Trias inférieur des Salt Ranges, Pakistan :problemèmes biochronologiques. Eclogae Geologicae Helvetiae, 71: 105-141, Basel. doi : 10.5169 / seals-164720
  2. ↑ TimeScale Creator 5.0 download page
  3. ↑ 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. . @1@ 2Template: Webachiv / IABot / www.episodes.co.in
  4. ^ Series, Stages, Substages and Biozones of the Triassic System (1995)
  5. ↑ Zakharov, Yuri D. (1994): Proposals on revision of the Siberian standard for the Lower Triassic and candidate stratotype section and point for the Induan-Olenekian boundary. Albertiana, 14: 44-51, Utrecht PDF  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. .@1@ 2Template: Dead Link / work.geobiology.cn  
  6. ↑ Galfetti, Thomas, Peter A. Hochuli, Arnaud Brayard, Hugo Bucher, Helmut Weissert & Jorunn Os Vigran: Smithian-Spathian boundary event: Evidence for global climatic change in the wake of the end-Permian biotic crisis. Geology, 34 (4): 291-294 doi : 10.1130 / G23117A.1

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

Web links