Calabrian is a subdivision of the Pleistocene

Pleistocene

The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 Epoch

Epoch (geology)

An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...

 of the Geologic time scale

Geologic time scale

The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...

. ~1.8 Ma.—781,000 years ago ± 5,000 years, a period of ~.

The end of the stage is defined by the last magnetic pole reversal

Geomagnetic reversal

A geomagnetic reversal is a change in the Earth's magnetic field such that the positions of magnetic north and magnetic south are interchanged. The Earth's field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse...

 (781,000 ± 5,000 Ka) and plunge in to an ice age and global drying possibly colder and drier than the late Miocene (Messinian

Messinian

The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ± 0.005 Ma and 5.332 ± 0.005 Ma...

) through early Pliocene (Zanclean

Zanclean

The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 and 3.6 Ma ± 0.005 Ma . It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age....

) cold period. Originally the Calabrian was a European faunal stage

Faunal stage

In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...

 primarily based on mollusk fossils. It has become the second geologic age in the Early Pleistocene. Many of the mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

ian faunal assemblages of the Early Pleistocene start in the Gelasian

Gelasian

The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma and 1.806 ± 0.005 Ma...

. For example, the Platygonus

Platygonus

Platygonus is an extinct genus of herbivorous peccary of the family Tayassuidae, endemic to North America from the Miocene through Pleistocene epochs , existing for approximately ....

 and other Blancan

Blancan

The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...

 fauna appear first in the Gelasian.

History of the definition of the Calabrian

Because sea shells are much more abundant as fossils, Nineteenth and early Twentieth Century geo-scientists used the plentiful and well-differentiatable Mollusca

Mollusca

The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...

 (mollusks) and Brachiopod

Brachiopod

Brachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...

s to identify stratigraphic

Stratigraphy

Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....

 boundaries. Thus the Calabrian was originally defined as an assemblage of mollusk fossils, most brachiopods being extinct by then. Efforts were then made to find the best representation of that assemblage in a stratigraphic section. By 1948 scientists used the initial appearance of cool-water (northern) invertebrate faunas in Mediterranean marine sediments as the beginning marker for the Calabrian. The 18th International Geological Congress in London (1948) placed the base of the Pleistocene at the base of the marine strata of the Calabrian Faunal Stage and denominated a type section

Global Boundary Stratotype Section and Point

A Global Boundary Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon stratigraphic section which serves as the reference section for a particular boundary on the geologic time scale. The effort to define GSSPs is conducted by the International Commission on...

 in southern Italy

Mezzogiorno

The Midday is a wide definition, without any administrative usage, used to indicate the southern half of the Italian state, encompassing the southern section of the continental Italian Peninsula and the two major islands of Sicily and Sardinia, in addition to a large number of minor islands...

. However, it was discovered that the original type section was discontinuous at that point and that the base of the Calabrian Stage as defined by fauna assemblages extended to earlier levels within the Pleistocene. A new type section was chosen, several miles from the original one, at Vrica, 4 km south of Crotone

Crotone

Crotone is a city and comune in Calabria, southern Italy, on the Ionian Sea. Founded circa 710 BC as the Achaean colony of Croton , it was known as Cotrone from the Middle Ages until 1928, when its name was changed to the current one. In 1994 it became the capital of the newly established...

 in Calabria

Calabria

Calabria , in antiquity known as Bruttium, is a region in southern Italy, south of Naples, located at the "toe" of the Italian Peninsula. The capital city of Calabria is Catanzaro....

, southern Italy. Analysis of strontium

Strontium

Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...

 and oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 isotope

Isotope

Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

s as well as of plankton

Plankton

Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

ic foraminifera

Foraminifera

The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

 has confirmed the viability of the current type section. The 27th International Geological Congress in Moscow in 1984 formally ratified the type section. The starting date was originally thought to be about 1.65 million years ago, but has been recalculated as 1.806 Mya.

Present formal definition

The Global Boundary Stratotype Section and Point, GSSP, for the start of the Pleistocene is in a reference section at Vrica, 4 km south of Crotone in Calabria, Southern Italy, a location whose exact dating has recently been confirmed by analysis of strontium and oxygen isotopes as well as by planktonic foraminifera.

The beginning of the Calabrian hence is defined as: Just above top of magnetic polarity chronozone C2n (Olduvai) and the extinction level of calcareous nannofossil Discoaster

Discoaster

Discoaster is a genus of fossil haptophytes.- Species :Some species in this genus include:*D. asymmetricus Gartner*D. bellus Bukry and Percival*D. berggrenii Bukry*D. bollii Martini and Bramlette...

 brouweri (base Zone CN13). Above the boundary are the lowest occurrence of calcareous nannofossil medium Gephyrocapsa

Gephyrocapsa

Gephyrocapsa is a genus of haptophytes.- Species :Species include:*G. caribbeanica*G. crassipons*G. ericsonii*G. kamptneri*G. muellerae*G. oceanica*G. ornata...

 spp. and the extinction level of the planktonic foraminifer Globigerinoides extremus.

The end of the Calabrian is defined as the Brunhes–Matuyama magnetic reversal event.