Rhaetium

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system series step ≈ age ( mya )
higher higher higher younger
Triad Upper Triassic Rhaetium 201.3
⬍
208.5
Norium 208.5
⬍
228
Carnium 228
⬍
235
Middle Triassic Ladinium 235
⬍
242
Anisium 242
⬍
247.2
Lower Triassic Olenekium 247.2
⬍
251.2
Indusium 251.2
⬍
251.9
deeper deeper deeper older

The Rhaetium ( Rhät , also Rät ) is an internationally used geological stage of the Upper Triassic , which covers the period about 208.5 to 201.3 million years ago and thus lasted about 7.2 million years. The rhaetium is the last (youngest) stage of the Triassic and follows the norium . The rhaetium is followed by the hettangium .

Naming and history

The Rhaetium is named after the Rhaetian Alps (old spelling Rhaetian Alps) in Eastern Switzerland and the adjacent border area between Italy and Austria. It was proposed by Carl Wilhelm von Gümbel in 1859 ("rhaetian formation").

Definition and GSSP

The basis of the rhaetium has not yet been clearly established; the deepest (first) ammonite zone of the rhaetium is Sagenites reticulatus in the Tethys area . This ammonite does not occur in the boreal area. Here the zone of the Cochloceras amoenum is the deepest ammonite zone of the Rhaetium. In addition, the conodonts Misikella spp. and Epigondolella mosheri , as well as the radiolarian species Proparvicingula moniliformis . The upper limit is also uncertain, as the GSSP for the beginning of the Jura has not been conclusively defined. The uppermost ammonite zone of the rhaetium is the zone of the Choristoceras marshi in the Tethys area . However, up to the base of the well-defined Psiloceras planorbis zone of the Hettangian ( Lower Jurassic ) there is a transition area (so-called “praeplanorbis layers”), which can probably be further subdivided. The Triassic / Jurassic border will probably be defined in this transition area.

Subdivision of the Rhaetium

In the Tethys area, the rhaetium is divided into two ammonite zones.

literature

  • Carl Wilhelm Gümbel: About equating the rock masses in the north-eastern Alps with non-alpine flötz layers. Official report on the fourth and thirtieth gathering of German natural scientists a. Doctors in Carlsruhe in September 1858, (34), pp. 80-88, Eisenlohr and Volz, Karlsruhe 1859. GoogleBooks
  • Peter Brack, Hans Rieber, Alda Nicora, Roland Mundil: 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): pp. 233-244, Beijing 2005 ISSN  0705-3797 .
  • Felix Gradstein, Jim Ogg, Jim & Alan Smith: A Geologic timescale. Cambridge University Press 2004, ISBN 978-0-521-78673-7
  • Leo Krystyn, S. Richoz, Y. Gallet, H. Bouquerel, WM Kürschner and C. Spötl: Updated bio- and magnetostratigraphy from Steinbergkogel (Austria), candidate GSSP for the base of the Rhaetian stage. Albertiana, 36: pp. 164-172, Utrecht 2007 PDF

Web links