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 geochronol ...
, the Kimmeridgian is an
age
Age or AGE may refer to:
Time and its effects
* Age, the amount of time someone or something has been alive or has existed
** East Asian age reckoning, an Asian system of marking age starting at 1
* Ageing or aging, the process of becoming older ...
in the
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987.
In European lithostratigraphy, the name ...
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 by ...
and a
stage
Stage or stages may refer to:
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 British theatre newspaper
* Sta ...
in the Upper Jurassic
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 ...
. It spans the time between 157.3 ± 1.0
Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the
Oxfordian and precedes the
Tithonian
In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...
.
Stratigraphic definition
The Kimmeridgian Stage takes its name from the village of
Kimmeridge
Kimmeridge () is a small village and civil parish on the Isle of Purbeck, a peninsula on the English Channel coast in Dorset, England. It is situated about south of Wareham and west of Swanage. In 2013 the estimated population of the civil p ...
on the
Dorset
Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset (unitary authority), Dors ...
coast,
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
. The name was introduced into the literature by French geologist
Alcide d'Orbigny
Alcide Charles Victor Marie Dessalines d'Orbigny (6 September 1802 – 30 June 1857) was a French naturalist who made major contributions in many areas, including zoology (including malacology), palaeontology, geology, archaeology and anthrop ...
in 1842.
The
Kimmeridge Clay Formation
The Kimmeridge Clay is a sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation is the major source rock for North ...
takes its name from the same
type location (although this formation extends from the Kimmeridgian stage of the Upper Jurassic into the Lower Cretaceous). It is the source for about 95% of the
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
in the
North Sea
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...
.
Historically, the term Kimmeridgian has been used in two different ways. The base of the interval is the same but the top was defined by British
stratigrapher
Stratigraphy is a branch of geology concerned with the study of rock layers ( strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.
Stratigraphy has three related subfields: lithostrat ...
s as the base of the
Portlandian
The Portland Group (defining the Portlandian) is a Late Jurassic ( Tithonian) lithostratigraphic group (a sequence of rock strata) in South East England. The name is derived from the Isle of Portland in Dorset where the strata are exposed and ...
(''sensu anglico'') whereas in France the top was defined as the base of the Tithonian (''sensu gallico''). The differences have not yet been fully resolved; Tithonian is the uppermost stage of the Jurassic in the timescale of the
ICS.
The base of the Kimmeridgian is at the first appearance of
ammonite
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...
species ''
Pictonia baylei'' in the
stratigraphic column
A stratigraphic column is a representation used in geology and its subfield of stratigraphy to describe the vertical location of rock units in a particular area. A typical stratigraphic column shows a sequence of sedimentary rocks, with the oldest ...
.
The
Global Boundary Stratotype Section and Point
A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted b ...
(GSSP) for the base of the Kimmeridgian is the Flodigarry section at
Staffin Bay on the
Isle of Skye
The Isle of Skye, or simply Skye (; gd, An t-Eilean Sgitheanach or ; sco, Isle o Skye), is the largest and northernmost of the major islands in the Inner Hebrides of Scotland. The island's peninsulas radiate from a mountainous hub dominated ...
,
Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
,
which was ratified in 2021. The boundary is defined by the first appearance of ammonites marking the boreal Bauhini Zone and the subboreal Baylei Zone.
The top of the Kimmeridgian (the base of the Tithonian) is at the first appearance of ammonite species ''
Hybonoticeras hybonotum''. It also coincides with the top of
magnetic anomaly
In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying ...
M22An.
Subdivision
The Kimmeridgian is sometimes subdivided into Upper and Lower substages. In the
Tethys domain, the Kimmeridgian contains seven
ammonite
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...
biozone
In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa, as opposed to a lithostratigraphic unit which is defined by the lithological properties of ...
s:
*zone of ''
Hybonoticeras beckeri''
*zone of ''
Aulacostephanus eudoxus''
*zone of ''
Aspidoceras acanthicum''
*zone of ''
Crussoliceras divisum''
*zone of ''
Ataxioceras hypselocyclum''
*zone of ''
Sutneria platynota''
*zone of ''
Idoceras planula''
References
Notes
Literature
*; 2004: ''A Geologic Time Scale 2004'',
Cambridge University Press
Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by Henry VIII of England, King Henry VIII in 1534, it is the oldest university press
A university press is an academic publishing hou ...
.
*; 1832: ''Sur Les Soulèvemens Jurassiques Du Porrentruy: Description Géognostique de la Série Jurassique et Théorie Orographique du Soulèvement'', Mémoires de la Société d'histoire naturelle de Strasbourg 1: pp 1–84, F. G. Levrault, Paris.
External links
GeoWhen Database - KimmeridgianJurassic-Cretaceous timescale at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic chart of the Upper Jurassic at the website of Norges Network of offshore records of geology and stratigraphy
{{Geological history, p, m
*02
Geological ages