Paleoproterozoic

Source: Wikipedia, the free encyclopedia.
Paleoproterozoic
2500 – 1600 Ma
stromatolites
Chronology
Proposed redefinition(s)2420–1780 Ma
Gradstein et al., 2012
Proposed subdivisionsOxygenian Period, 2420–2250 Ma

Gradstein et al., 2012
Jatulian/Eukaryian Period, 2250–2060 Ma
Gradstein et al., 2012
Columbian Period, 2060–1780 Ma

Gradstein et al., 2012
Etymology
Name formalityFormal
Alternate spelling(s)Palaeoproterozoic
Usage information
Celestial body
Era
Stratigraphic unitErathem
Time span formalityFormal
Lower boundary definitionDefined Chronometrically
Lower GSSA ratified1991[1]
Upper boundary definitionDefined Chronometrically
Upper GSSA ratified1991[1]

The Paleoproterozoic Era

geologic periods, namely the Siderian, Rhyacian, Orosirian and Statherian
.

Paleontological evidence suggests that the Earth's rotational rate ~1.8 billion years ago equated to 20-hour days, implying a total of ~450 days per year.[5] It was during this era that the continents first stabilized.[clarification needed]

Atmosphere

The

free oxygen levels soared permanently during the Siderian and Rhyacian periods in an aerochemical event called the Great Oxidation Event, which brought atmospheric oxygen from near none to up to 10% of the modern level.[7]

Life

At the beginning of the preceding

eukaryotic organisms
.

The Palaeoproterozoic represents the era from which the oldest cyanobacterial fossils, those of Eoentophysalis belcherensis from the Kasegalik Formation in the Belcher Islands of Nunavut, are known.[10]

Many crown node eukaryotes (from which the modern-day eukaryotic lineages would have arisen) have been approximately dated to around the time of the Paleoproterozoic Era.[11][12][13] While there is some debate as to the exact time at which eukaryotes evolved,[14][15] current understanding places it somewhere in this era.

fossils from the Changcheng Group in North China provide evidence that eukaryotic life was already diverse by the late Palaeoproterozoic.[19]

Geological events

During this era, the earliest global-scale continent-continent collision belts developed. The associated continent and mountain building events are represented by the 2.1–2.0 Ga Trans-Amazonian and

Akitkan Orogen in Siberia; the ~1.95 Ga Khondalite Belt; the ~1.85 Ga Trans-North China Orogen in North China; and the 1.8-1.6 Ga Yavapai and Mazatzal
orogenies in southern North America.

That pattern of collision belts supports the formation of a Proterozoic supercontinent named

Nuna.[20][21] That continental collisions suddenly led to mountain building at large scale is interpreted as having resulted from increased biomass and carbon burial during and after the Great Oxidation Event: Subducted carbonaceous sediments are hypothesized to have lubricated compressive deformation and led to crustal thickening.[22]

The lithospheric mantle of Patagonia's oldest blocks formed.[24]

See also

  • Boring Billion – Earth history, 1.8 to 0.8 billion years ago
  • Suavjärvi impact structure – Lake and claimed impact structure in Karelia, northwest Russia
  • Francevillian biota – Possible Palaeoproterozoic multicellular fossils from Gabon
  • Vredefort impact structure – Largest verified impact structure on Earth, about 2 billion years old
  • Sudbury Basin – Third largest verified astrobleme on earth, remains of an Paleoproterozoic Era impact
  • Neoarchean – Fourth era of the Archean Eon, which immediately preceded the Paleoproterozoic

References

External links