Chaotian (geology)

The Chaotian is a proposed time division of the geologic time scale. First proposed in 2010^[1] as an eon, it is named after Chaos, the primeval void in Greek mythology. This proposal defines the Chaotian eon as a Solar System-wide time between the initiation of planetary formation and the hypothesised collision of the trojan dwarf planet Theia with the proto-Earth.

Chaotian
4568 – 4404 Ma Pha. Proterozoic Archean Had.
Chronology
Subdivisions	See text
Usage information
Celestial body	Earth
Regional usage	Proposed subdivision of the Hadean eon
Definition
Chronological unit	Era
Stratigraphic unit	Erathem
First proposed by	C. Goldblatt, K. J. Zahnle, N. H. Sleep, and E. G. Nisbet, 2010
Lower boundary definition	Formation of the Earth
Upper boundary definition	Collision between Proto-Earth and the Protoplanet Theia

A revised proposal in 2012^[2] suggested the Chaotian as the first era of the Hadean representing the time between the formation of the Solar System c. 4.567 Ga^[3] and the oldest preserved crustal material on Earth, a detrital zircon c. 4.404 Ga^[4] from the Jack Hills of the Narryer terrane in Western Australia.

As of September 2023^[update], neither proposal had been adopted or officially ratified by the International Union of Geological Sciences.^[5]

Subdivisions

The original proposal in 2010 divided the Chaotian into two eras and four periods. No numerical upper age limits were provided, only the younger age limit of ~4.5 Ga for the boundary between the proposed Chaotian and Hadean boundary.

The revised proposal in 2012 did not subdivide the proposed Chaotian era (of the Hadean eon) into periods.

Proposed Chaotian time intervals (2010)^[1]

Eon	Era	Period	Age (Ga)
Chaotian	Neochaotian	Titanomachaen	> ~4.5
		Hyperitian
	Eochaotian	Erebrean
		Nephelean

Proposed Chaotian time intervals (2012)^[2]

Eon	Era	Age (Ga)
Hadean	Jack Hillsian or Zirconian	4.404 to 4.030
	Chaotian	4.568 to 4.404

See also

• Age of Earth
• Formation and evolution of the Solar System
• Geologic time scale