Geological dating wiki
Geologists tend to talk in terms of Upper/Late, Lower/Early and Middle parts of periods and other units, such as "Upper Jurassic", and "Middle Cambrian".
Upper, Middle, and Lower are terms applied to the rocks themselves, as in "Upper Jurassic sandstone," while Late, Middle, and Early are applied to time, as in "Early Jurassic deposition" or "fossils of Early Jurassic age." The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic." Because geologic units occurring at the same time but from different parts of the world can often look different and contain different fossils, there are many examples where the same period was historically given different names in different locales.
For example, the boundary between the Cretaceous period and the Palaeogene period is defined by the Cretaceous–Tertiary extinction event.
This marked the end of the dinosaurs and of many marine species.
The largest defined unit of time is the supereon composed of Eons.
Eons are divided into Eras, which are in turn divided into Periods, Epochs and Stages.
As above, this time scale is based on the International Commission on Stratigraphy.
While the term has several meanings, it usually refers to the act of ...
en.wikipedia.org/wiki/Datingrefers to seeking, arranging, and participating in meetings with potential intimate partners.
Dating may also refer to: absolute dating, such as using radiocarbon dating | dating methodologies in archaeology | relative dating, for example using ...
The remaining number of radioactive atoms is halved every half-life.
Radioactive elements of use in geological dating have relatively long half-lives.
For example, in North America the Lower Cambrian is called the Waucoban series that is then subdivided into zones based on trilobites.