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Stratigraphical natures for the Hadean:An important clue for understanding of both evolutionary history and palaeogeographical background in forming and initial periods of the Earth
Pages: 513-524
Year: Issue:  4
Journal: Journal of Palaeogeography

Keyword:  PrecambrianHadean EonChaotian EraZirconian Erastratigraphical nature;
Abstract: Within the current Precambrian geological time scale,it is an undefined base of the Arche-an Eon that it is roughly indicated at about 4000Ma,which results in a use of Hadean is informal as it has not been defined.Two of key advances led to the revision of stratigraphical nature for the Hedean,which as follows:(1 ) The discovery of truly ancient zircon crystal in Archean conglomerates at Jack Hills in Western Australia,which extend back to 4404Ma and contain a wealth of information about conditions on very early Earth;(2) The discovery of ca.4030Ma Acasta Gneiss in northern Canada.These discoveries,together with age dating of the Moon and meteorites,have yielded a great deal of knowledge about the early history of our solar system that is just an important foundation to revise the stratigraphical nature of the Hadean.The knowledge includes the formation of the solar system and the Earth,the important changes and their physical records on very early Earth,the origin of life and its early evolution.This revised Hadean Eon that has been recognized as the earliest period of Earth history,extends from the age of formation of the solar system at T0=4567Ma,to the age of Earth's oldest dated rock from the Acasta Gneiss Complex,at 4030Ma,and has further been subdivided into two eras:(1 ) the Chaotian Era (4567Ma-4404±8Ma);and (2)the Jack Hillsian Era or the Zirconian Era (4404 ±8Ma -4030 Ma).Both the lower (4567Ma) and upper (4030Ma) age limits for the Hadean Eon would necessarily be defined as chronometric boundaries,as there is no preserved stratigraphy.A Hadean Eon that has been endowed with a definitely stratigraphical na-ture not only delegates an important advance of studies on Precambrian stratigraphy,but also provides lots of important ideas for the further understanding of the evolutionary history of the early Earth.
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