The Coniacian is an

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone has been alive or something has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

stage Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...

in the

geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochron ...

. It is a subdivision of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

Epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cret ...

Series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used i ...

and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by the

Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...

and followed by the

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya ( million years ago) and 83.6 ± 0.7 m ...

Stratigraphic definitions

The Coniacian is named after the city of

Cognac Cognac ( , also , ) is a variety of brandy named after the Communes of France, commune of Cognac, France. It is produced in the surrounding wine-growing region in the Departments of France, departments of Charente and Charente-Maritime. Cogn ...

in the French region of

Saintonge Saintonge may refer to: *County of Saintonge, a historical province of France on the Atlantic coast * Saintonge (region), a region of France corresponding to the historical province * Saintonge ware, a medieval pottery type produced in Saintes reg ...

. It was first defined by French geologist

Henri Coquand Henri Coquand (1813, in Aix-en-Provence – 1881, in Marseille) was a French geologist and paleontologist. In 1841 he obtained his doctorate in sciences in Paris, and later served as a professor of geology at the University of Besançon, Poiti ...

in 1857. The base of the Coniacian Stage is at the first appearance of the

inoceramid The Inoceramidae are an extinct family (biology), family of bivalves ("clams") in the Class Mollusca. Fossils of inoceramids are found in marine sediments of Permian to latest Cretaceous in age. Inoceramids tended to live in upper bathyal and ner ...

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

species '' Cremnoceramus deformis erectus''. The official reference profile for the base (a

GSSP A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...

) is located in Salzgitter-Salder, Lower Saxony, Germany. The top of the Coniacian (the base of the Santonian Stage) is defined by the appearance of the inoceramid

Cladoceramus undulatoplicatus ''Cladoceramus'' is an extinct genus of fossil Marine (ocean), marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the Extant taxon, extant genus ''Pteria (bivalve), Pteria''. They lived in the Santoni ...

''. The Coniacian overlaps the regional Emscherian Stage of

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

, which is roughly coeval with the Coniacian and Santonian Stages. In

magnetostratigraphy Magnetostratigraphy is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their ' ...

, the Coniacian is part of

magnetic chronozone Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, m ...

C34, the so-called Cretaceous Magnetic Quiet Zone, a relatively long period with normal polarity.

Sequence stratigraphy and geochemistry

After a maximum of the global sea level during the early Turonian, the Coniacian was characterized by a gradual fall of the sea level. This cycle is in

sequence stratigraphy In mathematics, a sequence is an enumerated collection of mathematical object, objects in which repetitions are allowed and order theory, order matters. Like a Set (mathematics), set, it contains Element (mathematics), members (also called ''ele ...

seen as a first order cycle. During the middle Coniacian a shorter, second order cycle, caused a temporary rise of the sea level (and global transgressions) on top of the longer first order trend. The following regression (Co1, at 87,0 Ma) separates the Middle from the Upper Coniacian Substage. An even shorter third order cycle caused a new transgression during the Late Coniacian. Beginning in the Middle Coniacian, an

anoxic event An anoxic event describes a period wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O2), creating toxic, euxinic ( anoxic and sulfidic) waters. Although anoxic events have not happened for millions of years, the geol ...

(OAE-3) occurred in the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

, causing large scale deposition of

black shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g., kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...

s in the Atlantic domain. The anoxic event lasted till the Middle Santonian (from 87.3 to 84.6 Ma) and is the longest and last such event during the Cretaceous period.See Meyers ''et al.'' (2006)

Subdivision

The Coniacian is often subdivided into Lower, Middle and Upper Substages. It encompasses three

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

biozone In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxon, taxa, as opposed to a Lithostratigraphy, lithostratigraphic unit which is defined by the ...

s in the Tethys domain: * zone of '' Paratexanites serratomarginatus'' * zone of '' Gauthiericeras margae'' * zone of '' Peroniceras tridorsatum'' In the boreal domain the Coniacian overlaps just one ammonite biozone: that of '' Forresteria petrocoriensis.''

References

Notes

Literature

* ; 2004: ''A Geologic Time Scale 2004'',

Cambridge University Press Cambridge University Press was the university press of the University of Cambridge. Granted a letters patent by King Henry VIII in 1534, it was the oldest university press in the world. Cambridge University Press merged with Cambridge Assessme ...

. * ; 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, pp 1816–1830.

External links

GeoWhen Database - Coniacian

Late Cretaceous timescale
at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic chart of the Late Cretaceous
at the website of Norges Network of offshore records of geology and stratigraphy {{Geological history, p, m *03 Geological ages Cretaceous geochronology