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Precambrian Supereon

Precambrian.htm

A collection from Wikipedia: - https://en.wikipedia.org/wiki/Precambrian 180211
and other websites.

Downloaded and edited by U Kyaw Tun (UKT) (M.S., I.P.S.T., USA), and staff of Tun Institute of Learning (TIL) . Not for sale. No copyright. Free for everyone. Prepared for students and staff of TIL Research Station, Yangon, MYANMAR 
 - http://www.tuninst.net , www.romabama.blogspot.com

index.htm | | Top
geol-indx.htm

Contents of this page

Introduction

1.0. Overview
2.0. Life forms
3.0. Planetary environment and the oxygen catastrophe
4.0. Subdivisions
5.0. Precambrian super-continents
  Super-oceans

UKT 180213: Original references with active links to Wikipedia intact. Wiki references are in [...]. There are articles on this page which were not part of the original Wiki article.
UKT 180306: I have down loaded some interesting videos, such as those below which the are in the Geology section of TIL HD-VIDEO and SD-VIDEO libraries:
1. The Geological History of the Earth<ิ> / Bkp<ิ> (link chk 180306)
2. Geological History of Earth<ิ> / Bkp<ิ> (link chk 180306)

 

UKT notes
• Zircon dating

 

 

Contents of this page

Introduction

UKT 180306: Precambrian Supereon is the only supereon defined. The second supereon would be the one to which Pheneozoic Eon, and would belong.

From Wikipedia: - https://en.wikipedia.org/wiki/Precambrian 180211

The Precambrian Supereon or Pre-Cambrian, sometimes abbreviated , or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. [UKT ถ]

The Precambrian Supereon is so named because it preceded the Cambrian Period, the first Geologic Period of the Phanerozoic Eon. The Cambrian Period is named after Cambria, the Romanized Latinised name for Wales, where rocks from this age were first studied.

UKT 180211:
• As one working on BEPS languages, I must emphasize that Roman is the speech of the peoples of Rome, whereas Latin is the script used by the peoples of western Europe - the Romans (both ancient and modern) - and present day English-speakers, French-speakers, German-speakers, Italian-speakers, Spanish-speakers, etc., and peoples all over the world whose countries had been colonized by the British, French, Germans, Italians, Portuguese, and Spanish.
• Beware of different terminology given by other websites, e.g.
http://www.newworldencyclopedia.org/entry/Geologic_time_scale 180211
As a newcomer, I got confused with terminologies. Because of this, I wouldn't drop the suffixes and would write:
- Precambrian Supereon instead of Precambrian
- Hadean Eon instead of Hadean .

The Precambrian Supereon accounts for 88% of the Earth's geologic time. It is subdivided into three eons:

1. Hadean Eon,
2. Archean Eon,
3. Proterozoic Eon : the age of microbes - expressed macroscopically in colonial structures called stromatolites

The Precambrian Supereon spans from the formation of Earth about 4.6 Ga (billion years ago, or 4.6x10^9 yr ago)) to the beginning of the Cambrian Period, about 541 Ma (million years ago, or 541x10^6 yr ago), when hard-shelled creatures first appeared in abundance.

Contents of this page

1.0. Overview

Relatively little is known about the Precambrian Supereon, despite it making up roughly seven-eighths of the Earth's history, and what is known has largely been discovered from the 1960s onwards. The Precambrian Supereon fossil record is poorer than that of the succeeding Phanerozoic Eon, and fossils from that time (e.g. stromatolites) are of limited biostratigraphic use. [1] [UKTถ]

UKT 180304: Precambrian Supereon should be followed by another supereon, not by an eon. What is this supereon? This supereon would be the one to which Phanerozoic Eon belong. Look at the timeline below. Cambrian is a Period , far below in rank. No wonder I was confused!

The fossil record is poor because many Precambrian rocks [such as those from Proterozoic Eon], have been heavily metamorphosed, obscuring their origins, while others have been destroyed by erosion, or remain deeply buried beneath Phanerozoic strata. [1] [2] [3]

It is thought that the Earth coalesced from material in orbit around the Sun at roughly 4.5 Ga (4,543 Ma), and may have been struck by a very large (Mars-sized) planetesimal shortly after it formed, splitting off material that formed the Moon  [UKT ถ]
See Giant Impact hypothesis or the new variant which I have dubbed Titan Impact hypothesis based on names from mythology in History of the Earth - histearth.htm (link chk 180315).

A stable crust was apparently in place by 4.4 Ga (4,433 Ma) (i.e. in Hadean Eon, since zircon crystals from Western Australia have been dated at 4.4 Ga(4,404 ฑ 8 Ma.) [4]

UKT 180212: There are problems with Giant impact hypothesis. See the following downloads in TIL HD-PDF and SD-PDF libraries:
• Formation of the Moon: a new mechanism, by Mukesh Gupta*, 2014
- MGupta-MoonFormNewTh<ิ> / Bkp<ิ> (link chk 180212)
• Origin of the Moon - Giant Impact Hypothesis, NASA, 2014
- NASA-OriginMoonGiantImpact<ิ> / Bkp<ิ> (link 180212)
• Giant-impact hypothesis - https://en.wikipedia.org/wiki/Giant-impact_hypothesis 180305
"The giant-impact hypothesis, sometimes called the Big Splash, or the Theia Impact suggests that the Moon formed out of the debris left over from a collision between Earth and an astronomical body the size of Mars, approximately 4.5 Ga ago (billion years ago, 10^6 yr ago), in the Hadean eon; about 20 to 100 million years after the solar system coalesced. [1]"

Dating Zircon crystals:
See my notes below.
- From: https://www.amnh.org/explore/resource-collections/earth-inside-and-out/zircon-chronology-dating-the-oldest-material-on-earth/ 180305
"Originally formed by crystallization from a magma or in metamorphic rocks, zircons are so durable and resistant to chemical attack that they rarely go away. They may survive many geologic events, which can be recorded in rings of additional zircon that grow around the original crystal like tree rings. Like a tiny time capsule, the zircon records these events, each one of which may last hundreds of millions of years. Meanwhile, the core of the zircon itself remains unchanged, and preserves the chemical characteristics of the rock in which it originally crystallized.
   Zircon contains the radioactive element uranium, which Dr. Mueller* calls “the clock within the zircon” because it converts to the element lead at a specific rate over a long span of time. According to Mueller, this makes zircons “the most reliable natural chronometer that we have when we want to look at the earliest part of Earth history.” He goes on to explain that there are two ways to tell time in geology."
* Paul Mueller of the Univ. of Florida, and Darrell Henry of Louisiana State Univ. are involved in the study.

The term "Precambrian" is recognized by the ICS (International Commission on Stratigraphy) as the only "supereon" in geologic time; it is so called because it includes:
 #1. Hadean Eon (~4.6-4 billion),
 #2. Archean Eon (4-2.5 billion),
 #3. Proterozoic Eon (2.5 billion-541 million)
There is only one other eon which would belong to another supereon- still-in-making:
 #4. Phanerozoic Eon, 541 million-present.) [5] [UKT ถ]

UKT 180212: I wonder what this supereon-still-in-making would be called. See pdf pages in TIL HD-PDF and SD-PDF libraries:
• Two-phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity, by J. L. Payne, A. G. Boyer, J. H. Brown, S. Finnegan, M. Kowalewski, R. A. Krause, Jr., S. K. Lyonse, C. R. McClainf, D. W. McSheag, P. M. Novack-Gottshallh, F. A. Smithb, J. A. Stempien, and S. C. Wang, in PNAS, January 6, 2009, vol.106, no.1, 24-27.
- JLPayneEtAl-TwoPhaseIncreaseMaxSize<ิ> / Bkp<ิ> (link chk 180212)
• One of the authors of the above, Michał Kowalewski
( http://www.deepseanews.com/2011/05/on-the-reasons-why-we-need-a-new-supereon/ 180212) wrote:
"The largest unit of defined geologic time is the supereon. Only one is defined, the Precambrian spanning from the formation of the Earth to right before life goes crazy in the Cambrian explosion (4.6 Bya to 542 Mya).  Oddly, there is no other supereon after the Precambrian, just the Phanerozoic eon ranging from the Cambrian explosion to the present. ... Life as cyanobacteria first appears in the fossil record 3.5 billion years ago during the Acrhaean Eon. Molecular estimates place life starting around 3.97 Bya."

UKT 180212: - https://en.wikipedia.org/wyanobacteria 180212
"Cyanobacteria, aka Cyanophyta, are a phylum of bacteria that obtain their energy through photosynthesis, [4] and are the only photosynthetic prokaryotes able to produce oxygen. [5] ... 'Cyanobacteria are arguably the most successful group of microorganisms on earth. They are the most genetically diverse; they occupy a broad range of habitats across all latitudes, widespread in freshwater, marine, and terrestrial ecosystems, and they are found in the most extreme niches such as hot springs, salt works, and hypersaline bays. ...' - Stewart and Falconer [31]"

"Precambrian" is still used by geologists and paleontologists for general discussions not requiring the more specific eon names.

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2.0. Life forms

A specific date for the origin of life has not been determined. Carbon found in 3.8-billion-year-old rocks (Archean eon) from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have been found in Western Australia. [6] Probable fossils 100 million years older have been found in the same area. There is a fairly solid record of bacterial life throughout the remainder (Proterozoic eon) of the Precambrian Supereon.

Excluding a few contested reports of much older forms from North America and India, the first complex multicellular life forms seem to have appeared at roughly 1500 Ma, in the Neoproterozoic era of the Proterozoic eon. [UKT ถ]

The oldest fossil evidence from that era of such complex life comes from the Lantian formation of the Ediacarian period, at least 580 Mya. A very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota. Hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic era. [UKT ถ]

By the middle of the following Cambrian period, a very diverse fauna is recorded in the Burgess Shale, including some which may represent stem groups of modern taxa. The increase in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life. [7] [8]

UKT 180212: The so-called "Cambrian explosion of life" occurs approx. 541 Mya in the Cambrian period when most major animal phyla appeared in the fossil record. [2] [3] 
- https://en.wikipedia.org/wiki/Cambrian_explosion 180212
• A possible explanation is given by Richard J. Squire, Ian H. Campbell, Charlotte M. Allen, Christopher J.L. Wilson, in a paper titled Did the Transgondwanan Supermountain trigger the explosive radiation of animals on Earth?, 2006. See downloaded paper in TIL HD-PDF and SD-PDF libraries:
- RJSquireEtAl-TransgodwanaSupermountain<ิ> / Bkp<ิ> (link chk 180212)
• See also: Uplift of the central transantarctic mountains, by P. Wannamaker, G. Hill, J. Stodt, V. Maris, Y. Ogawa, K. Selway, G. Boren, E. Bertrand, D. Uhlmann, B. Ayling, A. M. Green & D. Feucht
- PWannamakerEtAl-UpliftCentralTransantarticMountains<ิ> / Bkp<ิ> (link chk 180212)
"East Antarctica is a stable, Precambrian cratonic shield that previously formed part of Rodinia and Gondwana supercontinents"

While land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. [9]

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3.0. Planetary environment and the oxygen catastrophe

Evidence of the details of plate motions and other tectonic activity in the Precambrian has been poorly preserved. It is generally believed that small proto-continents existed prior to 4280 Ma, and that most of the Earth's landmasses collected into a single supercontinent around 1130 Ma. The supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch, roughly 2400–2100 Ma. One of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a " Snowball Earth".

The atmosphere of the early Earth is not well understood. Most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and was lacking in free oxygen. There is, however, evidence that an oxygen-rich atmosphere existed since the early Archean Eon. [10]

At present, it is still believed that molecular oxygen was not a significant fraction of Earth's atmosphere until after photosynthetic life forms evolved and began to produce it in large quantities as a byproduct of their metabolism. [UKT ถ]

UKT 180305: The equation for photosynthesis states that the combination of carbon dioxide CO2, water H2O, and light energy [phtons] produces a carbohydrate (glucose) C6H12O6 and oxygen O2. Terrestrial life (organisms) needs free O2 for breathing, whereas aquatic life needs dissolved O2. The solubility of O2 in water depends on its salinity and temperature, and unless the Earth has cooled down enough, there is only scant dissolved O2 .

This radical shift from a chemically inert to an oxidizing atmosphere caused an ecological crisis, sometimes called the oxygen catastrophe. [UKT ถ]

UKT 180213: https://en.wikipedia.org/wiki/Great_Oxygenation_Event 180213
"The Great Oxygenation Event, the beginning of which is commonly known in scientific media as the Great Oxidation Event (GOE, also called the Oxygen Catastrophe, Oxygen Crisis, Oxygen Holocaust, [2] Oxygen Revolution, or Great Oxidation) was the biologically induced appearance of O2 in Earth's atmosphere. [3] Geological, isotopic, and chemical evidence suggest that this major environmental change happened around 2.45 Ga (billion years ago), [4] during the Siderian period, at the beginning of the Proterozoic eon. The causes of the event are not clear. [5] "

UKT 180305: https://en.wikipedia.org/wiki/Siderian 180305
"The Siderian Period (from sํdēros, meaning "iron") is the first geologic period in the Paleoproterozoic Era and lasted from 2500 Ma to 2300 Ma (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.
   The laying down of the banded iron formations (BIFs) peaked early in this period. BIFs were formed as anaerobic algae produced waste oxygen as O2 that combined with iron Fe, forming magnetite (Fe3O4, an iron oxide). This process cleared iron from the oceans, presumably turning greenish seas clear. Eventually, without an oxygen sink in the oceans, the process allowed the buildup of an oxygen-rich atmosphere. This event is known as the oxygen catastrophe, which, according to some geologists, triggered the Huronian glaciation. [1] [2]"

At first, oxygen would have quickly combined with other elements in Earth's crust, primarily iron, removing it from the atmosphere. After the supply of oxidizable surfaces ran out, oxygen would have begun to accumulate in the atmosphere, and the modern high-oxygen atmosphere would have developed. Evidence for this lies in older rocks that contain massive banded iron formations that were laid down as iron oxides.

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4.0. Subdivisions

UKT 180213: Don't forget : Supereon > Eon > Era > Period > Epoch > Age

A terminology has evolved covering the early years of the Earth's existence, as radiometric dating has allowed real dates to be assigned to specific formations and features. [11] The Precambrian Supereon is divided into three eons: the Hadean (4600–4000 Ma), Archean (4000-2500 Ma) and Proterozoic (2500-541 Ma). See Timetable of the Precambrian.

1.0.0 Proterozoic Eon: this eon refers to the time from the lower Cambrian boundary, 541 Ma, back through 2500 Ma. As originally used, it was a synonym for "Precambrian" and hence included everything prior to the Cambrian boundary. The Proterozoic eon is divided into three eras: the Neoproterozoic, Mesoproterozoic and Paleoproterozoic.

1.1.0. Neoproterozoic Era: The youngest geologic era of the Proterozoic Eon, from the Cambrian Period lower boundary (541 Ma) back to 1000 Ma. The Neoproterozoic corresponds to Precambrian Z rocks of older North American geology.

1.1.1. Ediacaran Period: The youngest geologic period within the Neoproterozoic Era. The "2012 Geologic Time Scale" dates it from 541 to 635 Ma. In this period the Ediacaran fauna appeared.
1.1.2. Cryogenian Period: The middle period in the Neoproterozoic Era: 635-720 Ma.
1.1.3. Tonian Period: the earliest period of the Neoproterozoic Era: 720-1000 Ma.

1.2.0. Mesoproterozoic Era: the middle era of the Proterozoic Eon, 1000-1600 Ma. Corresponds to "Precambrian Y" rocks of older North American geology.

1.3.0. Paleoproterozoic Era: oldest era of the Proterozoic Eon, 1600-2500 Ma. Corresponds to "Precambrian X" rocks of older North American geology.

2.0.0. Archean Eon: 2500-4000 Ma.

3.0.0. Hadean Eon: 4000–4600 Ma. This term was intended originally to cover the time before any preserved rocks were deposited, although some zircon crystals from about 4400 Ma demonstrate the existence of crust in the Hadean Eon. Other records from Hadean time come from the moon and meteorites. [12]

It has been proposed that the Precambrian Supereon should be divided into eons and eras that reflect stages of planetary evolution, rather than the current scheme based upon numerical ages. Such a system could rely on events in the stratigraphic record and be demarcated by GSSPs. The Precambrian Supereon could be divided into five "natural" eons, characterized as follows: [13]

1. Accretion and differentiation: a period of planetary formation until giant Moon-forming impact event.

2. Hadean: dominated by heavy bombardment from about 4.51 Ga (possibly including a Cool Early Earth period) to the end of the Late Heavy Bombardment period.>

3. Archean: a period defined by the first crustal formations (the Isua greenstone belt) until the deposition of banded iron formations due to increasing atmospheric oxygen content.

4. Transition: a period of continued iron banded formation until the first continental red beds.

5. Proterozoic: a period of modern plate tectonics until the first animals.

 

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5.0. Precambrian super-continents

The movement of Earth's plates has caused the formation and break-up of continents over time, including occasional formation of a super-continent containing most or all of the landmass. The earliest known super-continent was Vaalbara. It formed from proto-continents and was a super-continent 3.636 Ga ago (billion years ago). Vaalbara broke up c. 2.845–2.803 Ga ago. [UKT ถ]

The super-continent Kenorland was formed c. 2.72 Ga ago and then broke sometime after 2.45–2.1 Ga into the proto-continent cratons called Laurentia, Baltica, Australia, and Kalahari. The super-continent Columbia or Nuna formed 2.06–1.82 billion years ago and broke up about 1.5–1.35 Ga ago (billion years ago). [14] [15] [ not in citation given] The super-continent Rodinia is thought to have formed about 1.13–1.071 Ga ago (billion years ago), to have embodied most or all of Earth's continents and to have broken up into eight continents around 750–600 Ma ago (million years ago).

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Super-oceans

UKT 180213: Now that we know something of Supercontinents, we should know their counterpart - the Superoceans:
From: https://en.wikipedia.org/wiki/Superocean 180213

A superocean is an ocean that surrounds a supercontinent. It is less commonly defined as any ocean larger than the current Pacific Ocean. [1] Named global superoceans include Mirovia, which surrounded the supercontinent Rodinia, and Panthalassa, which surrounded the supercontinent Pangaea. Pannotia and Columbia, along with landmasses before Columbia (such as Ur and Kenorland), were also surrounded by superoceans.

[ 1] McMenamin, Mark A.; Dianna L. McMenamin. The Emergence of Animals. Columbia University Press. ISBN  0-231-06647-3.

As surface water moves unobstructed east to west in superoceans, it tends to warm from the exposure to sunlight so that the western edge of the ocean is warmer than the eastern. Additionally, seasonal changes in temperature, which would have been significantly more rapid inland, probably caused powerful monsoons. In general, however, the mechanics of superoceans are not well understood. [2]

[2] Martin, Ronald. "Cycles and Secular Trends". One Long Experiment. Columbia University Press. ISBN 0-231-10905-9.

Ancient superoceans:

• Nealbara/Gyrosia (Vaalbara/ Ur) (4.404–1.071 Ga)
• Lerova (Kenorland) (2.523–1.805 Ga)
• Atlanta-Pacifica Ocean (Columbia) (1.41–1.065 Ga)
• Mirovia (Rodinia) (1,380–600 Ma)
• Pan-African Ocean (Rodinia/ Pannotia) (987.5-605 Ma)
• Panthalassa ( Pannotia/ Pangaea) (750–173 Ma)

Possible future superoceans:
• Somali (12-803 Myr)
• Indo-Atlantic Ocean (Novopangaea/ Pangaea Ultima/ Amasia) (+65–283 Ma)

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UKT notes

Zircon dating

- UKT 180315: I will have to base my work on the two following sources.

- https://www.amnh.org/explore/resource-collections/earth-inside-and-out/zircon-chronology-dating-the-oldest-material-on-earth/ 180315

- https://www.sciencedirect.com/science/article/pii/S1674987114000577 180315

 

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