Update: 2018-02-15 07:04 PM -0500


Geologic time scale


from Wikipedia:
- https://en.wikipedia.org/wiki/Geologic_time_scale 180211

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

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UKT notes
See also: http://www.newworldencyclopedia.org/entry/Geologic_time_scale 180211


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From Wikipedia: https://en.wikipedia.org/wiki/Geologic_time_scale 180211

The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history. The tables of geologic time spans, presented here, agree with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy (ICS).

UKT 180215: Myanmarpré is a part of Asia. However, my motherland and the continent of Asia have never been the same throughout geological time stretching for about 4 billion years. To appreciate the changes, see downloaded videos in the TIL HD-VIDEO and SD-VIDEO libraries, in the folder GEOLOGY:
- Geological History of the World<Ô> / Bkp<Ô> (link chk 180215)
- A Brief History of Geologic Time<Ô> / Bkp<Ô> (link chk 180215)

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The primary defined divisions of time are eons, in sequence the Hadean, the Archean, the Proterozoic and the Phanerozoic. The first three of these can be referred to collectively as the Precambrian supereon. [UKT ¶]

Eons are divided into eras, which are in turn divided into periods, epochs and ages.

UKT 180211: 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 following four timelines show the geologic time scale. The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon. Therefore, the second timeline shows an expanded view of the most recent eon. [UKT ¶]

UKT 180211: Note the negative numbers in Millions of Years:
   -4500 millions of years = 4500 Ma. aka Mya (Millions of Years Ago.). Note also that only one supereon, the Precambrian, is defined.

In a similar way, the most recent era is expanded in the third timeline, and the most recent period is expanded in the fourth timeline.

UKT 180212: Geologic time scale is divided into Supereons, Eons, Eras, Periods, etc. depending on the size of the fossils, by :
See downloaded papers in TIL HD-PDF and SD-PDF libraries
- JLPayneEtAl-TwoPhaseIncreaseMaxSize<Ô> / Bkp<Ô> (link chk 180212)

Fig. 1. Sizes of the largest fossils through Earth history. Size maxima are illustrated separately for single-celled eukaryotes, animals, and vascular plants for the Ediacaran and Phanerozoic. The solid line denotes the trend in the overall maximum for all of life. Increases in the overall maximum occurred in discrete steps approximately corresponding to increases in atmospheric oxygen levels in the mid-Paleoproterozoic and Ediacaran–Cambrian–early Ordovician. Sizes of the largest fossil prokaryotes were not compiled past 1.9 Gya. Estimates of oxygen levels from Canfield (38) and Holland (37) are expressed in percentage of PAL. Phan., Phanerozoic; Pz., Paleozoic; Mz., Mesozoic; C, Cenozoic. Red triangles, prokaryotes; yellow circles, protists; blue squares, animals; green diamonds, vascular plants; gray square, Vendobiont (probable multicellular eukaryote).
  - Two-phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity, by Jonathan L. Payne, Alison G. Boyer, James H. Brown, Seth Finnegan, Michał Kowalewski, Richard A. Krause, Jr., S. Kathleen Lyonse, Craig R. McClainf, Daniel W. McSheag, Philip M. Novack-Gottshallh, Felisa A. Smithb, Jennifer A. Stempien, and Steve C. Wang, in PNAS, January 6, 2009, vol.106, no.1, 24-27.

UKT 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 billion years ago to 542 million years ago).  Oddly, there is no other supereon after the Precambrian, just the Phanerozoic eon ranging from the Cambrian explosion to the present.  The Precambrian can be broken into three eons, Hadean, Acrhaean, and Proterozoic.  Life as cyanobacteria first appears in the fossil record 3.5 billion years ago during the Acrhaean. Molecular estimates place life starting around 3.97 billion years ago."

Corresponding to eons, eras, periods, epochs and ages, the terms " eonothem", " erathem", " system", " series", " stage" are used to refer to the layers of rock that belong to these stretches of geologic time in Earth's history.

Geologists qualify these units as "early", "mid", and "late" when referring to time, and "lower", "middle", and "upper" when referring to the corresponding rocks. For example, the lower Jurassic Series in chronostratigraphy corresponds to the early Jurassic Epoch in geochronology. [2] The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic."

UKT: More in the Wiki artcle.

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UKT notes


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