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| Paleoproterozoic | |
|---|---|
| Name | Paleoproterozoic |
| Start | 2500 Ma |
| End | 1600 Ma |
| Period | Paleoproterozoic |
Paleoproterozoic is an interval of Earth's deep time spanning from about 2.50 to 1.60 billion years ago characterized by profound changes in geology, atmosphere, biosphere, and tectonics. This interval records the stabilization of many continental cratons such as Kaapvaal Craton, Slave Craton, and Pilbara Craton, major orogenic events like the Trans-Hudson orogeny and Wopmay orogeny, and global shifts including the Great Oxidation Event, the expansion of banded iron formation deposition, and the rise of early eukaryotic lineages. Research during this interval integrates data from institutions such as the Smithsonian Institution, United States Geological Survey, and Natural History Museum, London using methods refined by laboratories at Massachusetts Institute of Technology, University of California, Berkeley, and University of Cambridge.
The interval begins near the termination of the Archean Eon and predates the Mesoproterozoic Era, framed by stratigraphic units like the Transvaal Supergroup, Huronian Supergroup, and Roper Group. Chronostratigraphy relies on radiometric methods developed by teams at California Institute of Technology, Carnegie Institution for Science, and Australian National University employing U-Pb dating, Re-Os dating, and Sm-Nd isotopes on zircon, molybdenite, and whole-rock suites from units such as the Bushveld Complex, Hamersley Group, and Sucundu Formation. Global correlation uses marker events including_major glaciations recorded in the Makganyene glaciation, the Huronian glaciation, and excursions seen in the Shunga pyrite belt and Pahrump Group, tied to stratigraphic schemes maintained by the International Commission on Stratigraphy and regional surveys like the Geological Survey of Canada.
Tectonics of the interval feature accretion, collisional orogeny, and cratonization exemplified by the assembly of Laurentia through the Trans-Hudson orogeny and growth episodes recorded on the Yilgarn Craton, Rio de la Plata Craton, and Fennoscandian Shield. Plate interactions produced orogens such as the Svecofennian orogeny, Grenville orogeny (early phases), and the Yavapai orogeny, and led to the emplacement of large igneous provinces like the Gawler Craton flood basalts, Bitter Springs Formation sills, and the Daly River Complex. Metamorphism and magmatism generated mineralized belts including the Abitibi greenstone belt, Mawson Craton granitoids, and the Archean-Proterozoic boundary marked by cratonic root formation studied in cores from the Kola Superdeep Borehole and drilling projects by the Integrated Ocean Drilling Program.
Atmospheric shifts culminated in the Great Oxidation Event, which altered sulfur isotope systematics studied in samples from Gunflint Iron Formation, Nauga Formation, and Akatore Complex. Oxygenation drove deposition of banded iron formations in successions like the Banded Iron Formation (Hamersley), controlled carbon cycling recorded in carbonate units linked to the Shunga pyrite belt and organic-rich shales correlated with data from the Lamont–Doherty Earth Observatory and Woods Hole Oceanographic Institution. Paleoclimate episodes include multiple low-latitude glaciations inferred from diamictites in the Huronian Supergroup and glacial deposits correlated with strata in the Kalahari Craton and Transantarctic Mountains, with proxies refined at the Max Planck Institute for Chemistry and Scripps Institution of Oceanography.
Life during the interval is documented by microfossils, stromatolites, and biomarkers from localities such as the Bitter Springs Formation, Gunflint Iron Formation, and Kalamazoo Formation. The rise of oxygen enabled diversification of lineages leading toward eukaryotes with evidence from molecular clock analyses by researchers at University of Oxford, Harvard University, and Princeton University tying to fossils comparable with taxa described in the Proterozoic microfossils literature and collections at the Natural History Museum of Los Angeles County. Metabolic innovations include oxygenic photosynthesis by cyanobacteria inferred from stromatolite fabrics at Tumbiana Formation and sulfur cycling indicated by isotopic work from the Sakmarian deposits and the Eisenstadt Formation, while predation and cellular complexity are explored through analogs in the Ediacaran biota context and discussed at conferences of the Geological Society of America and American Geophysical Union.
This interval witnesses stabilization of cratons like the Kaapvaal Craton, Pilbara Craton, Superior Craton, Slave Craton, Baltic Shield, and North China Craton and major orogens including the Trans-Hudson orogeny, Svecofennian orogeny, Wopmay orogeny, and Yavapai orogeny. Assemblage hypotheses involve transient supercontinent cycles proposed in models by researchers at University of Toronto, University of Pretoria, and Peking University linking to configurations such as Columbia (supercontinent) (also called Nuna) assembly and breakup episodes, with stratigraphic evidence in the Glen Mountains, Mackenzie Large Igneous Province, and the Jasper Basin.
The interval hosts major mineral systems including banded iron formation deposits in the Hamersley Range, Siderite-rich ores in the Transvaal Supergroup, and base-precious metal mineralization in the Abitibi greenstone belt, Belt Supergroup, and Yukon-Tanana Terrane. Nickel-copper-platinum-group element sulfide ores occur in layered intrusions like the Bushveld Complex and Stillwater Complex analogs, while uranium and rare-earth element concentrations are found in Proterozoic pegmatites studied by companies such as Rio Tinto, BHP, and Anglo American. Exploration strategies derive from geophysical surveys by the United States Geological Survey, mineral databases at the British Geological Survey, and geochemical models developed at CSIRO and Geological Survey of Canada.
Scientific understanding has advanced through field studies by geologists associated with institutions such as the University of Cape Town, McGill University, and Monash University, and analytical advances at Lawrence Livermore National Laboratory and Oak Ridge National Laboratory. Methods include high-precision geochronology (U-Pb zircon) pioneered by teams at ETH Zurich, isotope geochemistry (S, C, Mo) refined at National Oceanography Centre, and paleomagnetic reconstructions from archives curated at the Natural History Museum, London. Major syntheses appear in journals published by the Geological Society of America, Nature Geoscience, and Journal of Geophysical Research and are debated at meetings hosted by the International Union of Geological Sciences and American Association of Petroleum Geologists.
Category:Geologic time