Cretaceous geochronology

second geologic series and epoch of the Cretaceous system and period

first geologic series and epoch of the Cretaceous system and period

The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from . The Maastrichtian was preceded by the Campanian and succeeded by the Danian (part of the Paleogene and Paleocene). It is named after the city of Maastricht, the capital and largest city of the Limburg province in the Netherlands.

The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian spans the time from 83.6 (± 0.2) to 72.2 (± 0.2) million years ago. It is preceded by the Santonian and it is followed by the Maastrichtian.

The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/Series. Its approximate time range is 113.2 ± 0.3 Ma to 100.5 ± 0.1 Ma (million years ago). The Albian is preceded by the Aptian and followed by the Cenomanian.

In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 137.05 ± 0.2 Ma and 132.6 ± 0.2 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretaceous and precedes the Hauterivian Stage of the Lower Cretaceous.

thumb|right|Palaeogeography of the Earth in Aptian. The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 0.6 Ma to 113.2 ± 0.3 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.

The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 0.6 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded by the Hauterivian and followed by the Aptian Stage.

The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding age. Both age and stage bear the same name.

The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.6 ± 0.6 Ma and 125.77 (million years ago). The Hauterivian is preceded by the Valanginian and succeeded by the Barremian.

The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.2 Ma and 89.8 ± 0.3 Ma (million years ago). The Turonian is preceded by the Cenomanian Stage and underlies the Coniacian Stage.

In the geological timescale, the Berriasian is an age or stage of the Early Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been estimated to span the time between 143.1 ± 0.6 and 137.05 ± 0.2 Ma (million years ago). The Berriasian succeeds the Tithonian (part of the Jurassic) and precedes the Valanginian.

The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 0.3 Ma and 85.7 ± 0.2 Ma (million years ago). The Coniacian is preceded by the Turonian 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 85.7 ± 0.2 mya (million years ago) and 83.6 ± 0.2 mya. The Santonian is preceded by the Coniacian and is followed by the Campanian.

In geology, Neocomian was a name given to the lowest stage of the Cretaceous system. It is generally considered to encompass the interval now covered by the Berriasian, Valanginian and Hauterivian, from approximately 145 to 130 Ma. It was introduced by Jules Thurmann in 1835 on account of the development of these rocks at Neuchâtel (Neocomum), Switzerland. It has been employed in more than one sense. In the type area the rocks have been divided into two sub-stages, a lower, Valanginian (from Valengin, Pierre Jean Édouard Desor, 1854) and an upper, Hauterivian (from Hauterive, Eugène Renevier,

fossil site in North Dakota, USA