Imbrian

Imbrian
Imbrian
3850 – 3200Ma PreN I N E C
Chronology
−4500 — – −4000 — – −3500 — – −3000 — – −2500 — – −2000 — – −1500 — – −1000 — – −500 — – 0 —	Pre-Nectarian Nectarian Imbrian Eratosthenian Copernican Late Early
	Periods on the Lunar Geologic Timescale. Axis scale: Millions of years ago.;
Usage information
Celestial body	Earth's Moon
Time scale(s) used	Lunar Geologic Timescale
Definition
Chronological unit	Period

TheImbrianis a lunar geologic period divided into two epochs, theEarlyandLate.

Early Imbrian

In thelunar geologic timescale,theEarly Imbrianepoch occurred from 3,850 million years ago to about 3,800 million years ago. It overlaps the end of theLate Heavy Bombardmentof theInner Solar System.Theimpactthat created the hugeMare Imbriumbasin occurred at the start of the epoch. The other large basins that dominate the lunar near side (such asMare Crisium,Mare Tranquillitatis,Mare Serenitatis,andMare Fecunditatis) were also formed in this period. These basins filled withbasaltmostly during the subsequent Late Imbrian epoch. The Early Imbrian was preceded by theNectarian.

Late Imbrian

Lunar olivine basalt formed around 3.3 billion years ago. This is part of sample 15555, known asGreat Scott.

In theLunar geologic timescale,theLate Imbrianepoch occurred between 3,800 million years ago to about 3,200 million years ago. It was theepochduring which themantlebelow the lunar basins partially melted and filled them withbasalt.The melting is thought to have occurred because the impacts of the Early Imbrian thinned the overlying rock – either causing the mantle to rise because of the reduced pressure on it, bringing molten material closer to the surface, or the top melting as heat flowed upwards through the mantle because of reduced overlyingthermal insulation.The majority of lunar samples returned to earth for study come from this epoch.^{[citation needed]}

Relationship to Earth's geologic time scale

Since little or nogeologicalevidence onEarthexists from the time spanned by the Early and Late Imbrian epoch of the Moon, the Early and Late Imbrian has been used by at least one notable scientific work^[1]as an unofficial subdivision of the terrestrialHadean eon.

References

^W. Harland; R. Armstrong; A. Cox; L. Craig; A. Smith; D. Smith (1990).A Geologic time scale 1989.Cambridge University Press.

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[1] W. Harland; R. Armstrong; A. Cox; L. Craig; A. Smith; D. Smith (1990).A Geologic time scale 1989.Cambridge University Press.

[1]

Imbrian

Contents

Early Imbrian

Late Imbrian

Relationship to Earth's geologic time scale

See also

References