Sinemurian
The Sinemurian (also Sinemurian, or more rarely, Sine Murien ) is in Earth's history, a chronostratigraphic stage of the Jura. In the geochronological division of geological history which roughly corresponds to the period from 199.3 to 190.8 million years ago. The Sinemurian following the Hettangian, it is detached from the Pliensbachian.
- 6.1 dinoflagellates
- 6.2 Calcareous nannoplankton
Naming and history
The Sinemurian was named after the Latin name Sinemurum Briennense castrum of Semur -en- Auxois (Dept. Côte -d'Or in Burgundy ( France). Stage and the name were proposed by Alcide Dessalines d' Orbigny, 1842.
Definition and GSSP
The beginning of the Sinemuriums is defined by the first appearance of the ammonite genera Vermiceras and Metophioceras. The upper limit (and therefore the lower limit of the Pliensbachiums ) is the first occurrence of the ammonite species Bifericeras donovani and the ammonite genus Apoderoceras. For GSSP ( = " Global Stratotype Section and Point" is roughly equivalent to a type profile ) has a profile in a cliff was determined north of the village East Quantoxhead. The village is situated about 6 km east of Watchet (Somerset, England).
Subdivision of Sinemuriums
- Echioceras raricostatum
- Oxynocticeras oxynotum
- Asteroceras obtusum
- Caenisites turneri
- Arnioceras semicostatum
- Arietites buck landi
The Sinemurian is composed of two sub- stages, the upper Sinemurian is designated regional ( derived from Lorraine) as Lotharingium. The boundary between the two sub-stages located at the base of Asteroceras obtusum Ammonites zone.
Sea level
The sea level generally showed an upward trend in the Sinemurian. In lay down a pattern of transgression - regression - transgression. The regression Si 3 lies on the border from the lower to the upper Sinemurian, the first transgression culminating in the Arnioceras semicostatum Ammonites zone, the second at the turn of the Pliensbachian.
Chemical stratigraphy
Carbon isotopes
The δ13C values increase from its minimum to 1 ‰ (PDB ) at the beginning of Sinemuriums to a maximum value at 4 ‰ at the beginning of Lotharingiums on, and then falling back to 2 ‰ at the end of the stage. The increase is associated with increased organic carbon production.
Oxygen isotopes
The values of δ18O are generally rising slightly, from - 2 ‰ (PDB ) to - 1 ‰. This suggests steady, gradual cooling during the Sinemuriums.
Strontium isotopes
The ratio 87Sr/86Sr in seawater declined sharply, from 0.7077 to 0.7074. This indicates reduced continentality or increased volcanic activity, probably related to the opening North Atlantic.
Biostratigraphy
Dinoflagellates
In the boreal region forms the Sinemurian part of the upper Dinoflagellatenzone Dpr and the lower portion of Lva (or zones DSJ1, DSJ2 and DSJ3 ). The upper limit is the level of the cyst Liasidium variable defined by the last-time occurrence ( LAD). Her last appearance further the cyst Dapcodinium has priscum at the end of Caenisites turneri Ammonites zone), the same occurs here Liasidium variable for the first time ( FAD).
Calcareous nannoplankton
The Sinemurian is one of the Nannoplanktonzonen NJ2a, NJ2b and NJ3. At the beginning of the stage for the first time appears the taxon Parhabdolithus liasicus. At the beginning of NJ2b Parhabdolithus disappears marthae. The lower limit of NJ3 is defined by the first publication of Crepidolithus crassus.
Foraminifera
The following taxa occur in the lower Foraminiferenzone: Lenticulina inaequistriata, Ichthyolaria muelensis and Ichthyolaria sulcata. Furthermore, present in this zone are Denticulina faciata and Nodosaria issleri (occur towards the end of Coroniceras buck landi zone for the first time ), Lenticulina quadricostatus tata ( disappears during Caenisites turneri zone) and Lenticulina radiata (occurs during Arnioceras semicostatum zone for the first on time ). The top portion can be reported at the beginning of the Echioceras raricostatum Ammonites zone Foraminiferenzone Marginulina spinata.
Fossils
The seas were populated by ichthyosaurs with the taxon Ichthyosaurus and the plesiosaurs with the taxa Eretmosaurus and Plesiosaurus.
On the mainland, the dinosaurs had held a dominant position. Among the bird Beck dinosaur ( Ornithischia ) to find Abrictosaurus, Fabrosaurus, Geranosaurus, Lanasaurus, Lusitanosaurus, Lycorhinus, Merosaurus, Scelidosaurus and Stormbergia. The theropods were represented by Dilophosaurus, Sarcosaurus and Saltriosaurus.
First early mammals are Hadrocodium and Kueneotherium.
Occurrence
Examples of formations of Sinemuriums with the associated Sedimentationsräumen are:
- Aquitanisches pool: Basal Transgressionssequenz of Hettangiums and Sinemuriums
- Paris Basin: Calcaire à gryphées, Argiles à Promicroceras and Calcaires ocreux - Luxembourg sandstone, Grès de Virton
- England: Blue Lias Formation, Charmouth Mudstone Formation -
- Northwest Germany: Arietiten layers Raricostaten layers
- Southern Germany: Arietitenkalk lineup, Obtususton lineup - Gryphäensandstein lineup
- Swiss Jura: Gryphitenkalk
- Northern Limestone Alps: Gresten lineup, Allgäu lineup spot or marl, Liaskieselkalk, Kalksburger layers Kirchsteinkalk, Eisenspitzbrekzie, Adnet Formation, Hierlatzkalk, Seibel mountain formation, Enzesfelder lime and Duerrenberg lineup
- Engadine window: Steinberger Lias
- Tauern window: Hochstegbrücke quartzite and quartzite Schwarzkopf
- Southern Karawanken: Rooster Kogel lineup
- Southern Alps: Gray Kieselkalke
- India: Kota Formation
- People's Republic of China: Lufeng Formation
- Cape Province, South Africa: Clarens Formation and Upper Elliot Formation
- Lesotho, South Africa: Upper Elliot Formation, Stormberg Series
- Zimbabwe: Forest Sandstone
- North America: Kayenta Formation