Imbrian

Short description: Lunar geologic period

Imbrian

Template:Lunar range
Chronology

Template:Lunar periods graphical timeline

Usage information
Celestial body| Earth's Moon
Time scale(s) used| Lunar Geologic Timescale
Definition
Chronological unit| Period

The Imbrian is a lunar geologic period divided into two epochs, the Early and Late.

## Contents

* 1 Early Imbrian
* 2 Late Imbrian
* 3 Relationship to Earth's geologic time scale
* 4 See also
* 5 References

## Early Imbrian

In the lunar geologic timescale, the Early Imbrian epoch occurred from 3,850 million years ago to about 3,800 million years ago. It overlaps the end of the Late Heavy Bombardment of the Inner Solar System. The impact that created the huge Mare Imbrium basin occurred at the start of the epoch. The other large basins that dominate the lunar near side (such as Mare Crisium, Mare Tranquillitatis, Mare Serenitatis, and Mare Fecunditatis) were also formed in this period. These basins filled with basalt mostly during the subsequent Late Imbrian epoch. The Early Imbrian was preceded by the Nectarian.

## Late Imbrian

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

In the Lunar geologic timescale, the Late Imbrian epoch occurred between 3,800 million years ago to about 3,200 million years ago. It was the epoch during which the mantle below the lunar basins partially melted and filled them with basalt. 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 overlying thermal insulation. The majority of lunar samples returned to earth for study come from this epoch.

The Earth equivalent consists of half of the Archean eon.

## Relationship to Earth's geologic time scale

Since little or no geological evidence on Earth exists 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 terrestrial Hadean eon.

## See also

* Hadean eon-related topics

## References

1. ↑ 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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Hadean Eon

* Cryptic
* Basin Groups
* Nectarian
* Lower Imbrian

The Hadean does not have any subdivisions recognized by the International Commission on Stratigraphy. These subdivisions represent one proposal that is loosely based on the lunar geologic timescale.

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Geological history of Earth

Cenozoic era
(present–66.0 Mya)|

| Quaternary (present–2.588 Mya)|

* Holocene (present–11.784 kya)
* Pleistocene (11.784 kya–2.588 Mya)

|

Neogene (2.588–23.03 Mya)|

* Pliocene (2.588–5.333 Mya)
* Miocene (5.333–23.03 Mya)

Paleogene (23.03–66.0 Mya)|

* Oligocene (23.03–33.9 Mya)
* Eocene (33.9–56.0 Mya)
* Paleocene (56.0–66.0 Mya)

Mesozoic era
(66.0–251.902 Mya)|

| Cretaceous (66.0–145.0 Mya)|

* Late (66.0–100.5 Mya)
* Early (100.5–145.0 Mya)

|

Jurassic (145.0–201.3 Mya)|

* Late (145.0–163.5 Mya)
* Middle (163.5–174.1 Mya)
* Early (174.1–201.3 Mya)

Triassic (201.3–251.902 Mya)|

* Late (201.3–237 Mya)
* Middle (237–247.2 Mya)
* Early (247.2–251.902 Mya)

Paleozoic era
(251.902–541.0 Mya)|

| Permian (251.902–298.9 Mya)|

* Lopingian (251.902–259.8 Mya)
* Guadalupian (259.8–272.3 Mya)
* Cisuralian (272.3–298.9 Mya)

|

Carboniferous (298.9–358.9 Mya)|

* Pennsylvanian (298.9–323.2 Mya)
* Mississippian (323.2–358.9 Mya)

Devonian (358.9–419.2 Mya)|

* Late (358.9–382.7 Mya)
* Middle (382.7–393.3 Mya)
* Early (393.3–419.2 Mya)

Silurian (419.2–443.8 Mya)|

* Pridoli (419.2–423.0 Mya)
* Ludlow (423.0–427.4 Mya)
* Wenlock (427.4–433.4 Mya)
* Llandovery (433.4–443.8 Mya)

Ordovician (443.8–485.4 Mya)|

* Late (443.8–458.4 Mya)
* Middle (458.4–470.0 Mya)
* Early (470.0–485.4 Mya)

Cambrian (485.4–541.0 Mya)|

* Furongian (485.4–497 Mya)
* Miaolingian (497–509 Mya)
* Series 2 (509–521 Mya)
* Terreneuvian (521–541.0 Mya)

Proterozoic eon
(541.0 Mya–2.5 Gya)|

| Neoproterozoic (541.0 Mya–1 Gya)|

* Ediacaran (541.0–~635 Mya)
* Cryogenian (~635–~720 Mya)
* Tonian (~720 Mya–1 Gya)

|

Mesoproterozoic (1–1.6 Gya)|

* Stenian (1–1.2 Gya)
* Ectasian (1.2–1.4 Gya)
* Calymmian (1.4–1.6 Gya)

Paleoproterozoic (1.6–2.5 Gya)|

* Statherian (1.6–1.8 Gya)
* Orosirian (1.8–2.05 Gya)
* Rhyacian (2.05–2.3 Gya)
* Siderian (2.3–2.5 Gya)

Archean eon (2.5–4 Gya)|

| Eras|

* Neoarchean (2.5–2.8 Gya)
* Mesoarchean (2.8–3.2 Gya)
* Paleoarchean (3.2–3.6 Gya)
* Eoarchean (3.6–4 Gya)

|

Hadean eon (4–4.6 Gya)|

|  |

|

kya = thousands years ago. Mya = millions years ago. Gya = billions years ago.
See also: Geologic time scale

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