Earth:Paleoarchean

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Short description: Second era of the Archean Eon
Paleoarchean
3600 – 3200 Ma
Chronology
Proposed redefinition(s)4031–3490 Ma
Gradstein et al., 2012
Proposed subdivisionsAcastan Period, 4031–3810 Ma

Gradstein et al., 2012
Isuan Period, 3810–3490 Ma

Gradstein et al., 2012
Etymology
Name formalityFormal
Alternate spelling(s)Palaeoarchaean
Synonym(s)Early Archean
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitEra
Stratigraphic unitErathem
Time span formalityFormal
Lower boundary definitionDefined Chronometrically
Lower boundary GSSPN/A
GSSP ratifiedN/A
Upper boundary definitionDefined Chronometrically
Upper boundary GSSPN/A
GSSP ratifiedN/A
A stromatolite formed by Paleoarchean miocrobial mats, preserved as a fossil, from Pilbara craton, Western Australia
Artist's impression of what Vaalbara may have looked like

The Paleoarchean (/ˌpliɑːrˈkən/), also spelled Palaeoarchaean (formerly known as early Archean), is a geologic era within the Archaean Eon. It spans the period of time 3,600 to 3,200 million years ago—the era is defined chronometrically and is not referenced to a specific level of a rock section on Earth. The name derives from Greek "Palaios" ancient. The oldest ascertained life form of fossilized bacteria in microbial mats, 3,480 million years old, found in the Dresser Formation in Western Australia, is from this era.[1][2] Vaalbara, one of Earth's earliest supercontinents, may have formed during this era.[3]

During this era, a large asteroid, about 37 to 58 kilometres (23–36 mi) wide, collided with the Earth in the area of Southern Africa about 3.26 billion years ago, creating the features known as the Barberton greenstone belt.[4]

A map of the Barberton Greenstone Belt in southern Africa

References

External links