Calabrian is a subdivision of the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

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 ...

of the

geologic time scale 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 geochr ...

, defined as 1.8 Ma—774,000 years ago ± 5,000 years, a period of ~. The end of the stage is defined by the last magnetic pole reversal (781 ± 5 Ka) and plunge into an ice age and global drying possibly colder and drier than the late Miocene ( Messinian) through early Pliocene (

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 ± 0.005 Ma (million years ago) and 3.6 ± 0.005 Ma. It is preceded by the Messinian Age of the Miocene Epoch, and ...

) cold period. Originally the Calabrian was a European

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 convent ...

primarily based on mollusk fossils. It has become the second geologic age in the Early Pleistocene. Many of the mammalian faunal assemblages of the Early Pleistocene start in the

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 2.58 Ma (million ye ...

. For example, the

Platygonus ''Platygonus'' ("flat head" in reference to the straight shape of the forehead) is an extinct genus of herbivorous peccaries of the family Tayassuidae, endemic to North and South America from the Miocene through Pleistocene epochs (10.3 million ...

and other Blancan fauna appear first in the Gelasian.

History of the definition of the Calabrian

Because sea shells are much more abundant as fossils, 19th- and early-20th-century geo-scientists used the plentiful and well-differentiatable Mollusca (mollusks) and

Brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

s to identify

stratigraphic 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: lithostra ...

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 The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...

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 A stratotype or type section in geology is the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the stan ...

in southern Italy. 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 in Calabria, southern Italy. Analysis of strontium and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...

s as well as of

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

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 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 ...

, for the former 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.Lourens, L., Hilgen, F., Shackleton, N.J., Laskar, J., Wilson, D., (2004) “The Neogene Period”. In: Gradstein, F., Ogg, J., Smith, A.G. (Eds.), Geologic Time Scale Cambridge University Press, Cambridge; 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'' is a genus of extinct star-shaped marine algae, with calcareous exoskeletons of between 5-40 μm across that are abundant as nanofossils in tropical deep-ocean deposits of Neogene age. ''Discoaster'' belongs to the haptophyt ...

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

Notes

References

* {{DEFAULTSORT:Calabrian (Stage) Pleistocene geochronology Geological ages Pleistocene Europe Quaternary geochronology

History of the definition of the Calabrian

Present formal definition

See also

Notes

References