The Rhyacian Period (; , meaning "stream of
lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
") is the second
geologic period
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronolo ...
in the
Paleoproterozoic
The Paleoproterozoic Era (also spelled Palaeoproterozoic) is the first of the three sub-divisions ( eras) of the Proterozoic eon, and also the longest era of the Earth's geological history, spanning from (2.5–1.6 Ga). It is further sub ...
Era and lasted from Mya to Mya (million years ago).
Instead of being based on
stratigraphy
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.
Stratigraphy has three related subfields: lithost ...
, these dates are defined
chronometrically.
The
Bushveld Igneous Complex
The Bushveld Igneous Complex (BIC) is the largest Layered intrusion, layered igneous intrusion within the Earth's Crust (geology), crust. It has been tilted and Erosion, eroded forming the outcrops around what appears to be the edge of a great Ba ...
and some other similar
intrusion
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
s formed during this period.
The
Huronian (Makganyene) global glaciation began at the start of the Rhyacian and lasted 100 million years. It lasted about 80% of this period.
For the time interval from 2250 Ma to 2060 Ma, an alternative period based on stratigraphy rather than chronometry, named either the Jatulian or the Eukaryian, was suggested in the geological timescale review 2012 edited by Gradstein et al.,
but , this has not yet been officially adopted by the
IUGS
The International Union of Geological Sciences (IUGS) is an international non-governmental organization devoted to global cooperation in the field of geology. As of 2023, it represents more than 1 million geoscientists around the world.
About
Fo ...
. The term Jatulian is, however, used in the regional stratigraphy of the Paleoproterozoic rocks of
Fennoscandia
__NOTOC__
Fennoscandia (Finnish language, Finnish, Swedish language, Swedish and ; ), or the Fennoscandian Peninsula, is a peninsula in Europe which includes the Scandinavian Peninsula, Scandinavian and Kola Peninsula, Kola peninsulas, mainland ...
.
This is when the
eukaryotes
The eukaryotes ( ) constitute the domain of Eukaryota or Eukarya, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of ...
are thought to have originated from the symbiosis between
asgardarchaea and
alphaproteobacteria
''Alphaproteobacteria'' or ''α-proteobacteria'', also called ''α-Purple bacteria'' in earlier literature, is a class of bacteria in the phylum '' Pseudomonadota'' (formerly "Proteobacteria"). The '' Magnetococcales'' and '' Mariprofundales'' ar ...
, as well as the
sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...
found within the eukaryotes only, thus the alternative name Eukaryian.
Macroscopic life is discovered to have started during the Rhyacian period.
[https://phys.org/news/2024-07-complex-life-earth-began-billion.html]
References
Paleoproterozoic
Geological periods
Proterozoic geochronology
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