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The Mesoproterozoic Era is a
geologic Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following peri ...

geologic
era An era is a span of time defined for the purposes of chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronology Chronology (from Latin Latin (, or , ) is a classical language belonging t ...
that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the
Paleoproterozoic The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Year, Ga), is the first of the three sub-divisions (era (geology), eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest ...
), but little is known about them. The continental masses of the Mesoproterozoic were more or less the same ones that exist today.


Major events and characteristics

The major events of this era are the breakup of the Columbia supercontinent, the formation of the
Rodinia Rodinia (from the Russian родить, ''rodit'', meaning "to beget, to give birth", or родина, ''rodina'', meaning "motherland, birthplace") was a Neoproterozoic supercontinent that assembled 1.1–0.9 billion years ago and broke up 750 ...

Rodinia
supercontinent In geology Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers sim ...
, and the evolution of
sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, ...
. This era is marked by the further development of continental plates and
plate tectonics Plate tectonics (from the la, label=Late Latin Late Latin ( la, Latinitas serior) is the scholarly name for the written Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. L ...
. The first large-scale mountain building episode, the
Grenville Orogeny The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent Orogeny, orogenic belt which spans a significant portion of the North American co ...
, for which extensive evidence still survives, happened in this period. This era was the high point of the
Stromatolites Stromatolites () or stromatoliths () are layered sedimentary formation of rocks, formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing microorganism, sulfate-reducing bacteria ...

Stromatolites
before they declined in the
Neoproterozoic The Neoproterozoic Era is the unit of geologic time The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such ob ...
. The era saw the development of sexual reproduction, which greatly increased the complexity of life to come. It was the start of development of communal living among organisms, the
multicellular organisms Multicellular organisms are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties of life. It is a synonym for "Out ...
. It was an era of apparently critical, but still poorly understood, changes in the chemistry of the sea, the
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...

sediment
s of the earth, and the composition of the air.
Oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

Oxygen
levels had risen to perhaps 1% of today's levels at the beginning of the era and continued rising throughout the Era. The era did see large quantities of organisms in at least some areas at some periods: The EIA/ARI ''Technically Recoverable Shale Oil and Shale Gas Resources: An Assessment of 137 Shale Formations in 41 Countries Outside the United States'' of June 2013 estimated around 194 trillion cubic feet of gas in place (ca. 44 trillion recoverable) and around 93 billion barrels of oil in place (ca. 4.7 billion recoverable) in the Lower Kyalla and Middle Velkerri formations alone of the Beetaloo Basin in Australia's Northern Territory.U. S. Energy Information Administration/Advanced Resources International, ''Technically Recoverable Shale Oil and Shale Gas Resources: An Assessment of 137 Shale Formations in 41 Countries Outside of the United States'', June 2013, p. III-46. The Lower Kyalla and Middle Velkerri formations are identified as Mesoproterozoic in references, p. III-49.


Subdivisions

The subdivisions of the Mesoproterozoic are arbitrary divisions based on time. They are not
geostratigraphic
geostratigraphic
or
biostratigraphic Biostratigraphy is the branch of stratigraphy through Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic period million years ago (Year, Mya ...
units. The base of the Mesoproterozoic is defined chronometrically, in terms of years, rather than by the appearance or disappearance of some organism. This gives an illusory sense of certainty.
Radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "di ...
is a good tool, and gets better each decade. This creates some problems. As a practical matter, radiometric dates have an error margin of 1–2%. That sounds good, but it means that two sites, both measured to be at the exact base of the
Ectasian The Ectasian Period (from Greek ἔκτασις ''(éktasis)'', meaning "extension") is the second geologic period in the Mesoproterozoic Era and lasted from Mya ago to Mya (million years ago). Instead of being based on stratigraphy throug ...
, might differ in age by over 50 My. Since the Ectasian is only 200 My long, these differences dramatically influence its timescale. And this accounts only for random error, ignoring systematic errors. Systematic errors can be caused by extraterrestrial events, by geochemical or biochemical sorting of isotopes, and human error. Thus far,
biostratigraphy Biostratigraphy is the branch of stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sed ...
has usually proved considerably more exact. In addition, a thoughtful choice of biological marker can be used as a signal to expect a whole host of
ecological Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms In biology ...
changes. The difference between a
Changhsingian In the geologic time scale, the Changhsingian or Changxingian is the latest age (geology), age or uppermost stage (stratigraphy), stage of the Permian. It is also the upper or latest of two subdivisions of the Lopingian Epoch (geology), epoch or se ...
and an
Induan The Induan is the first age of the Early Triassic The Early Triassic is the first of three epoch (geology), epochs of the Triassic Period (geology), Period of the geologic timescale. It spans the time between annum, Ma and Ma (million years ...
deposit isn't just a matter of a few years. The world changed significantly at the end of the Permian. By contrast, the transition from
Calymmian The Calymmian Period (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately ...
to Ectasian has no meaning beyond calendar time. The usual reason given for the use of a chronometric system is that there is insufficient biological activity or geochemical change to find useful markers. That is a position which is now a little uncertain and is going to become increasingly tenuous over the next few years. For example, there are a number of good potential markers in the rise and decline of "Christmas tree" stromatolites, in the ebb and flow of
banded iron formation Banded iron formations (also known as banded ironstone formations or BIFs) are distinctive units of sedimentary rock consisting of alternating layers of iron oxides and iron-poor chert. They can be up to several hundred meters in thickness a ...

banded iron formation
s, the appearance of stable
carbon-13 isotope
carbon-13 isotope
(13C) excursions, and so on. These have real meaning for the geologist and paleontologist. For that matter, they are not completely without biological markers. There has been considerable progress in studying and identifying fossil bacteria and Eukarya. The
cyanobacterium Cyanobacteria , also known as Cyanophyta, are a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical ca ...

cyanobacterium
Archaeoellipsoides is one relatively common form, apparently known from several species. It is probably related to the extant
Anabaena ''Anabaena'' is a genus of Filamentation, filamentous cyanobacteria that exist as plankton. They are known for nitrogen-fixing abilities, and they form symbiosis, symbiotic relationships with certain plants, such as the mosquito fern. They are one ...
and indicates the presence of significant free oxygen. Oxygen levels also had significant effects on
ocean chemistry Ocean chemistry, also known as marine chemistry, is influenced by plate tectonics and seafloor spreading, turbidity Ocean current, currents, sediments, pH levels, atmosphere, atmospheric constituents, Metamorphic reaction, metamorphic activity, ...
; continental weathering rates increased and provided
sulfate The sulfate or sulphate ion is a polyatomic anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having ...

sulfate
s and
nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalently bonded A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the format ...

nitrate
s as nutrients. It would be remarkable if this didn't result in new populations of both bacterial and
eukaryotic Eukaryotes () are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...
organisms. Since the presence of these cells would be tied directly to important geochemical events, they would make ideal organisms for biostratigraphy. The time period from 1780 Ma to 850 Ma, an unofficial period based on
stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

stratigraphy
rather than
chronometry Chronometry (from Ancient Greek, Greek χρόνος ''chronos'', "time" and μέτρον ''metron'', "measure") is the science of the measurement of time, or timekeeping. And with the measurement, chronometry employs the standardisation of time a ...
, named the Rodinian, is described in the geological timescale review 2012 edited by Gradstein et al., but , this has not yet been officially adopted by the
International Union of Geological Sciences The International Union of Geological Sciences (IUGS) is an international non-governmental organization A non-governmental organization, or simply an NGO, is an that is, generally, formed independent from . They are typically s, and many o ...
(IUGS).


See also

*
Boring Billion The Boring Billion, otherwise known as the Barren Billion, the Dullest Time in Earth's History, and Earth's Middle Ages, is the time period between 1.8 and 0.8 billion years ago (Gya) spanning the middle Proterozoic The Proterozoic () is a geolo ...


References


External links


Mesoproterozoic (chronostratigraphy scale)
{{Authority control Geological eras