Dating geologic time

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Knowing that a certain rock was deposited in the “Pennsylvanian”, for example, may help the PG to interpret rocks in a certain area.

Also, petroleum geologists are mainly interested in rocks from the Mesozoic and Paleozoic Eras.

A controversial issue during the first decade of the 21st century was the position of the base of the Quaternary System/Period and its status as a formal division of time.

After much debate, the International Union of Geological Sciences formally ratified a new definition of the base of the Quaternary and the corresponding base of the Pleistocene Series/Epoch, changing its age from 1.806 Ma to 2.588 Ma (see box for age terms) (Gibbard and others, 2010).

Another change to the time scale is the age of the base of the Holocene Series/Epoch.

The boundary is now defined on the basis of an abrupt climate change recorded by indicators in a Greenland ice core (Walker and others, 2009). For many years, the term "Precambrian" was used for the division of time older than the Phanerozoic.

1), which represents an update containing the unit names and boundary age estimates ratified by the International Commission on Stratigraphy (ICS). North American Commission on Stratigraphic Nomenclature, 2005, North American stratigraphic code: American Association of Petroleum Geologists Bulletin, v.

But of course, these oil and gas-bearing rocks represent only a small fraction of the total age of the earth, which is measured in billions of years.

Geologic Time Scale: Divisions of Geologic Time approved by the U. It reflects ratified unit names and boundary estimates from the International Commission on Stratigraphy (Ogg, 2009). * Changes to the time scale since March 2007 (see text). URL: Effective communication in the geosciences requires consistent uses of stratigraphic nomenclature, especially divisions of geologic time.

By modern scientific calculations, the earth is many millions of years old.

The Absolute Geologic Time Scale has been developed by using a process called “Isotopic Dating”, in which the decay rates of certain radioactive materials are established and measured, then used as “clocks” to calculate the ages of various rocks.

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