Coniacium
system | series | step | ≈ age ( mya ) |
---|---|---|---|
higher | higher | higher | younger |
chalk | Upper Chalk | Maastrichtium | 66 ⬍ 72 |
Campanium | 72 ⬍ 83.6 |
||
Santonium | 83.6 ⬍ 86.3 |
||
Coniacium | 86.3 ⬍ 89.7 |
||
Turonium | 89.7 ⬍ 93.9 |
||
Cenomanium | 93.9 ⬍ 100.5 |
||
Lower Cretaceous | Albium | 100.5 ⬍ 112.9 |
|
Aptium | 112.9 ⬍ 126.3 |
||
Barremium | 126.3 ⬍ 130.7 |
||
Skin rivium | 130.7 ⬍ 133.9 |
||
Valanginium | 133.9 ⬍ 139.3 |
||
Berriasium | 139.3 ⬍ 145 |
||
deeper | deeper | deeper | older |
The Coniacium (in German usage often shortened to Coniac) is a chronostratigraphic level of the Upper Cretaceous in the history of the earth . It can be dated geochronologically to the period from approx. 89.7 to approx. 86.3 million years. The coniac follows the turonium and is replaced by the santonium .
Naming and history
The rock units typical for this stage are located in the historic Saintonge landscape near the city of Cognac ( Charente department , France). Henri Coquand introduced the level and name to scientific literature in 1857.
Definition and GSSP
The lower limit of the level is defined by the first appearance of the Inoceramen species Cremnoceramus rotundatus (identical to Cremnoceramus deformis erectus ), the upper limit by the first appearance of the Inoceramen species Cladoceramus undulatoplicatus . A GSSP (global type locality and type profile of the lower level limit) for the Coniacium has not yet been made binding. The Salzgitter-Salder limestone quarry is a promising candidate .
Breakdown
The coniacium is divided into lower, middle and upper coniacium at the lower level.
The coniacium together with the santonium formed the stratigraphic level of the Emscher .
In Tethysbereich for Coniacian be biostratigraphically three ammonite zones excreted:
In the boreal area, the Forresteria petrocoriensis zone appears at the bottom .
Magnetostratigraphy
The entire coniacium belongs magnetostratigraphically to the C34 anomaly, the so-called "Cretaceous magnetic calm zone" with normal polarity.
Sea level cycles
After reaching the absolute maximum sea level in the Unterturon , a gradual renewed decline in the sea level becomes noticeable in the Coniacium . However, this 1st order cycle is overlaid by a shorter-period sea level rise (2nd order cycle), which leads to transgressions globally and culminates in the central coniacium. This is followed by the regression Co1 (87.0 Ma BP), which separates the middle and upper coniacium from one another. A third order cycle also causes a new transgression in the upper coniacium.
Oceanic anoxic event
From the Central Coniacian onwards, an oceanic anoxic event occurs in the Atlantic area with the formation of black slate sediments , the so-called OAE-3 , which lasts into the Central Cantonium (87.3 - 84.6 Ma BP). It is the longest and last such event during the Cretaceous Period.
Individual evidence
- ↑ Meyers, PA, Bernasconi, SM, Forster, A., 2006. Origins and accumulation of organic matter in expanded Albian to Santonian black shale sequences on the Demerara Rise, South American margin. Organic Geochemistry 37, 1816-1830.
literature
- Felix Gradstein, Jim Ogg, Jim & Alan Smith: A Geologic timescale. Cambridge University Press 2004 ISBN 978-0-521-78673-7
- Hans Murawski & Wilhelm Meyer: Geological dictionary . 10., rework. u. exp. Ed., 278 p., Enke Verlag, Stuttgart 1998 ISBN 3-432-84100-0 .
Web links
- German Stratigraphic Commission, Manfred Menning (Hrsg.): Stratigraphische Tisch von Deutschland 2002 . Potsdam 2002, ISBN 3-00-010197-7 (1 sheet, Stratigraphie.de [PDF; 6.6 MB ]).
- Commission for the paleontological and stratigraphic research of Austria of the Austrian Academy of Sciences (Ed.): The Stratigraphic Table of Austria (sedimentary layer sequences). Vienna 2004 (PDF; 376 kB)
- International Chronostratigraphic Chart 2012 (PDF)