Stratigraphic System

a basic subdivision of the international stratigraphic scale corresponding to a natural stage in the development of the earth’s crust and the organic world. The interval of time during which a system is formed is called a geological period. In the recent history of the earth, that is, in the Phanerozoic eon, 12 systems are distinguished. Their order was established in the first half of the 19th century and was accepted in 1881 in Bologna at the second session of the International Geological Congress.