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Many of the dominant taxonomic groups present in modern times can be ultimately traced back to origins in the Cretaceous. During this time, new groups of mammals and birds appeared, including the earliest relatives of placentals & marsupials (Eutheria and Metatheria respectively), with the earliest crown group birds appearing towards to the end ...
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 geochronology (a scientific branch of geology that aims to determine the age of rocks).
Geologic time is the timescale used to calculate dates in the planet's geologic history from its origin (currently estimated to have been some 4,600 million years ago) to the present day. Radiometric dating measures the steady decay of radioactive elements in an object to determine its age. It is used to calculate dates for the older part of ...
In the geological timescale, the Berriasian is an age/stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 143.1 ±0.6 Ma and 137.05 ± 0.2 (million years ago). [2] The Berriasian succeeds the Tithonian (part of the Jurassic) and precedes the Valanginian.
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 creta, the Latin word for the white limestone known as chalk.
Mid-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS (The top of the Albian stage is also still visible on their Late Cretaceous timescale) Stratigraphic chart of the Lower Cretaceous, at the website of Norges Network of offshore records of geology and stratigraphy
The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma [2] (Historically, this stage was placed at 129.4 million to approximately 125 million years ago [3]) It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series).
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 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by the Cenomanian Stage and underlies the Coniacian Stage. [3]