The Neoarchean (; also spelled Neoarchaean) is the last
geologic era in the
Archean eon that spans from 2800 to 2500 million years ago—the period being defined
chronometrically and not referencing a specific level in a rock section on
Earth. The era is marked by major developments in complex life and continental formation.
Complex life
This era saw the rise of oxygen in the atmosphere after
oxygenic photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...
evolved as early as the
Mesoarchean era.
The environmental changes that occurred in the Neoarchean such as its developing atmospheric and soil compositions drastically differentiated the era from others in its encouragement of
microbial metabolisms to evolve and diversify.
The era could have also seen pre-biotic organic molecules being brought to Earth through
meteorites,
comets, or through abiotic reactions.
The growth of juvenile
continental crust as well as the onset of
plate tectonics in the Archean allowed for the colonization of a larger variety of niches by
microorganisms through increasing the number of rock types present and thereby increasing the surface's chemical diversity.
Some noted metabolisms were able to flourish due to changes in the availability of certain metals while others faced famine: an increase in
copper present in the environment in the Neoarchean likely favored
aerobic metabolisms.
Oxygenic photosynthesis may have been limited earlier in the Archean era from a lack of
phosphorus stemming from poor biological recycling in
anaerobic conditions.
This issue was alleviated in the Neoarchean with the abundance of phosphorus in
magmatic rocks, which when combined with other evolving
geodynamics such as increasing organic matter burial and higher oxidative states in volcanic sulfur and magmatic iron contributed to a large buildup of oxygen in the atmosphere, leading to the
Great Oxidation Event in the
Paleoproterozoic era.
Continental formation
During this era, the supercontinent
Kenorland
Kenorland was one of the earliest known supercontinents on Earth. It is thought to have formed during the Neoarchaean Era c. 2.72 billion years ago (2.72 Ga) by the accretion of Neoarchaean cratons and the formation of new continental crust. ...
is proposed to have formed about 2.7 billion years ago.
Kenorland is of particular interest due to it containing deposits of
volcanic-hosted massive sulphide,
gold, and
uranium found in the
Canadian Shield. With new research, the validity of Kenorland has been questioned in favor of other Neoarchean supercontinent proposals Superia or
Vaalbara.
Improved geologic knowledge suggests that a part of Kenorland, specifically the
Churchill Province, was instead a continental development that formed after the Neoarchean era,
Nuna, closer to 1.9 billion years ago.
This challenge to the reconstruction is based on research studying northern Kenorland's Paleoproterozoic cover as well as the suture between the
Rae and
Hearne Cratons.
The
supercontinent cycle can be studied through patterns that describe how Earth's crust and its mineral deposits were preserved over time since
Pangaea.
Plate tectonics, having developed earlier in the Archean eon,
produced the force necessary for
metamorphism and
magmatic activity
Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of ...
which greatly contributed to these continental changes.
Research on how the supercontinents broke apart and combined into different configurations is involved in linking together deep-interior and surface-level processes as well as the assessment of contrasting models of early Paleoproterozoic geodynamic activity.
References
External links
Neoarchean (chronostratigraphy scale)
{{Geological history, c
*04
Geological eras
Precambrian geochronology