Sinemurium

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system series step ≈ age ( mya )
higher higher higher younger
law Upper Jurassic Tithonium 145
⬍
152.1
Kimmeridgium 152.1
⬍
157.3
Oxfordium 157.3
⬍
163.5
Middle Jurassic Callovium 163.5
⬍
166.1
Bathonium 166.1
⬍
168.3
Bajocium 168.3
⬍
170.3
Aalenium 170.3
⬍
174.1
Lower Jurassic Toarcium 174.1
⬍
182.7
Pliensbachium 182.7
⬍
190.8
Sinemurium 190.8
⬍
199.3
Hettangium 199.3
⬍
201.3
deeper deeper deeper older

The Sinemurium (also Sinemur , or more rarely also Sinemuria) is a chronostratigraphic level of the Jurassic in the history of the earth . In the geochronological classification of the earth's history, this roughly corresponds to the period from 199.3 to 190.8 million years. The Sinemurium follows the Hettangium , it is replaced by the Pliensbachium .

Naming and history

The Sinemurium was named after the Latin name Sinemurum Briennense castrum by Semur-en-Auxois ( Département Côte-d'Or ) in Burgundy (France). The stage and name were suggested by Alcide Dessalines d'Orbigny in 1842.

Definition and GSSP

Cliff near the GSSP at East Quantoxhead

The beginning of the Sinemuriums is the first appearance of ammonite genera Vermiceras and Metophioceras set. The upper limit (and thus the lower limit of the Pliensbachium) forms the first occurrence of the ammonite species Bifericeras donovani and the ammonite genus Apoderoceras . For the GSSP (= "Global Stratotype Section and Point", corresponds roughly to a type profile), a profile was determined in a cliff north of the village of East Quantoxhead . The village is about 6 km east of Watchet ( Somerset , England ).

Subdivision of the Sinemurium

Arietites bucklandi from Balingen

In the Tethys area, the Sinemurium is subdivided biostratigraphically into six ammonite zones (from hanging to lying):

The Sinemurium is made up of two lower stages, the upper Sinemurium also being regionally known as the Lotharingium (derived from Lorraine ). The boundary between the two sub-stages is at the base of the Obtusum Zone.

Sea level

The sea ​​level in the Sinemurium showed a generally rising tendency. A pattern of transgression-regression-transgression lay over it. The regression Si 3 lies on the border between the lower and upper Sinemurium, the first transgression culminates in the Arnioceras semicostatum ammonite zone, the second at the turn of the Pliensbachian.

Chemical stratigraphy

Carbon isotopes

The δ 13 C values ​​rise from their minimum by 1 ‰ (PDB) at the beginning of the Sinemurium to a maximum value of 4 ‰ at the beginning of the Lotharingium, and then fall back to 2 ‰ at the end of the stage. The increase is associated with increased organic carbon production.

Oxygen isotopes

The values ​​for δ 18 O are generally slightly increasing, namely from - 2 ‰ (PDB) to - 1 ‰. This indicates a steady, gradual cooling in the course of the Sinemurium.

Strontium isotopes

The ratio of 87 Sr / 86 Sr in seawater fell sharply, from 0.7077 to 0.7074. This indicates decreased continentality or increased volcanic activity, probably in connection with the opening North Atlantic .

Biostratigraphy

Dinoflagellates

In the boreal area, the sinemurium forms part of the upper dinoflagellate zone Dpr and the lower section of Lva (or zones DSJ1 , DSJ2 and DSJ3 ). The upper limit of the stage is defined by the last occurrence ( LAD ) of the Liasidium variable cyst . The last appearance of the cyst Dapcodinium priscum at the end of the Caenisites turneri ammonite zone, at the same time Liasidium variable appears here for the first time ( FAD ).

Calcareous nannoplankton

The Sinemurium belongs to the nannoplankton zones NJ2a , NJ2b and NJ3 . At the beginning of the stage, the taxon Parhabdolithus liasicus appears for the first time . At the beginning of NJ2b, Parhabdolithus marthae disappears . The lower limit of NJ3 is defined by the first appearance of Crepidolithus crassus .

Foraminifera

Three foraminiferous zones can be distinguished for the sinemurium . In the lower one occur: Lenticulina inaequistriata , Ichthyolaria muelensis and Ichthyolaria sulcata . Also present in this zone are Denticulina fasciata and Nodosaria issleri (appear for the first time towards the end of the Coroniceras bucklandi zone), Lenticulina quadricostata (disappears during the Caenisites turneri zone) and Lenticulina radiata (occurs first during the Arnioceras semicostatum zone Times on). In the middle section, the foraminiferous zone Marginulina spinata can be identified with the beginning of the Echioceras raricostatum ammonite zone . Shortly before the end of the Sinemurium, a third zone, not yet designated, begins, which leads into the Pliensbachium.

Two zones could be seen in the Großforms. The lower zone is dominated by the involutina liassica . The upper zone is shared by Lituosepta compressa , Orbitopsella praecursor and Paleomayncina termieri , which appear for the first time with the beginning of the Asteroceras obtusum zone.

Fossils

Abrictosaurus

The seas were populated by the ichthyosaurs with the taxa Ichthyosaurus , Leptonectes and Temnodontosaurus and the plesiosaurs with the taxa Eretmosaurus and Plesiosaurus .

On the mainland, the dinosaurs held a dominant position. Abrictosaurus , Fabrosaurus , Geranosaurus , Lanasaurus , Lusitanosaurus , Lycorhinus , Merosaurus , Scelidosaurus , Stormbergia and Tatisaurus are found among the bird pelvic dinosaurs ( Ornithischia ) . The theropods were represented by Dilophosaurus , Sarcosaurus , Saltriosaurus and Sinosaurus .

Within the class of synapsids , the Cynodontia Bienotherium should be mentioned.

The first early mammals are Hadrocodium and Kueneotherium .

Occurrence

Obtususton from Hüttlingen

Examples of formations of the Sinemurium with the associated sedimentation spaces are:

Individual evidence

  1. ^ Michael J. Benton: Prehistoric Life . Dorling Kindersley, Edinburgh, Scotland 2012, ISBN 978-0-7566-9910-9 , pp. 44-45 .

literature

  • Gert Bloos and Kevin N. Page: Global Stratotype Section and Point for base of the Sinemurian Stage (Lower Jurassic) . In: Episodes . tape 25 (1) . Beijing 2001, p. 22-28 . PDF
  • Felix Gradstein, Jim Ogg, Jim & Alan Smith: A Geologic timescale . Cambridge University Press, 2005, ISBN 978-0-521-78673-7 .
  • Hans Murawski & Wilhelm Meyer: Geological dictionary. 10., rework. u. exp. Ed., 278 . Enke Verlag, Stuttgart 1998, ISBN 3-432-84100-0 .
  • Alcide d´Orbigny: Paléontologie française. 1. Terrains oolitiques or jurassiques . Bertrand, Paris 1842, p. 642 .

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