Proterozoic
Aeonothem | Arathem | system | Age ( mya ) |
---|---|---|---|
later | later | later | |
P r o t e r o z o i k u m Duration: 1959 Ma |
Neoproterozoic Jungproterozoikum Duration: 459 Ma |
Ediacarium | 541 ⬍ 635 |
Cryogenium | 635 ⬍ 720 |
||
Tonium | 720 ⬍ 1000 |
||
Mesoproterozoic Mittelproterozoikum Duration: 600 Ma |
Stenium | 1000 ⬍ 1200 |
|
Ectasium | 1200 ⬍ 1400 |
||
Calymmium | 1400 ⬍ 1600 |
||
Paleoproterozoic Altproterozoikum Duration: 900 Ma |
Statherium | 1600 ⬍ 1800 |
|
Orosirium | 1800 ⬍ 2050 |
||
Rhyacium | 2050 ⬍ 2300 |
||
Siderium | 2300 ⬍ 2500 |
||
earlier | earlier | earlier |
The Proterozoic (composed of the Greek words πρότερος próteros , German 'previous' , 'early' and ζῶον zôon , German 'living being' ), formerly also called Algonkian or Eozoic , is an aeon of geological development in the Precambrian . It ranges from the end of the Archean , around 2500 million years ago to around 541 million years ago.
History and naming
The term Proterozoic was first proposed in its English form as Proterozoic by Samuel Franklin Emmons at the 5th International Geological Congress. He referred to the temporal position of clastic formations between the Archean and the Cambrian. The name was intended to indicate that the living environment documented in these formations appears earlier than that of the Paleozoic Era without having to commit to the fact that these were the first traces of life at all.
the atmosphere
The Proterozoic is characterized by the presence of an oxygen-containing atmosphere . Already towards the end of the Archean , before 2500 mya, the oxygen content in the earth's atmosphere began to rise. Although the production of oxygen by photosynthesizing organisms had already started around a billion years earlier, it was only from this point in time that oxygen was released into the atmosphere. Previously, this process was the oxygen uptake during the oxidation of the dissolved inorganic substances in sea water, in particular iron - ions and ions of other heavy metals is prevented. These metal ions, present in the reduced state, were oxidized to metal oxides in the course of time, only then could free oxygen enter the atmosphere. With increasing oxygen concentration in the atmosphere, ozone could also be formed, which was able to filter UV light that is harmful to living beings . Only oxygen made the development of animal life possible.
The climate was also at times significantly different from today; there are indications of global icing ( Snowball Earth , Snowball Earth ).
Development of life
The name Proterozoic indicates that it is the time of the beginning of animal life. Fossil remains of living things, which are difficult to assign to the animal phyla known today, have been found. Since these first animal forms had hardly any skeletons or hard shells, many morphological structures have not been preserved and their forms are difficult to reconstruct. In addition, the fossil-bearing strata were exposed to geological changes over time. Strange communities, such as those preserved in the fossils of the well-known Ediacaran fauna , formed in the shallow, warm seas near the coast. With the end of the Proterozoic at the turn of the Cambrian , most of the tribes of the animal kingdom seem to have already been present as the exit for the Cambrian explosion that followed.
Subdivision of the Proterozoic
It is divided into the following aera topics :
- Eon : Phanerozoikum (541-0 mya )
- Eon : Proterozoic (2500-541 mya)
- Era : Neoproterozoic (1000-541 mya)
- Era: Mesoproterozoic (1600–1000 mya)
- Era: Paleoproterozoic (2500–1600 mya)
- Eon: Archean (4000-2500 mya)
- Eon: Hadean (4600-4000 mya)
An alternative structure looks like this:
- Sinium (800-545 mya)
- Riphaeic (1,650-800 mya)
- Animicium (2,200-1,650 mya)
- Huronium (2,450-2,200 mya)
See also
Web links
- Volker Mosbrugger : Lecture in WS 2000/2001 (video) . It can be found under “Faculty of Mathematics and Natural Sciences”, “Geosciences”, “Paleobiology”. Topics: historical geology ; Proterozoic; Grypania ; Acritarches ; Vendium [since 2004: Ediacarium ]; Ediacaran Faunas . timms (Tübingen Internet Multimedia Server). ZDV University of Tübingen, November 10, 2000
- Proterozoic. Entry in the encyclopedia of geosciences on Spektrum.de
Individual evidence
- ↑ SF Emmons: Letter to Persifor Frazer, dated May 25, 1887 . In: International Geology Congress, American Committee Reports . Philadelphia 1988, p. A58 (English).