Rodinium

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The Rodinium is the fourth period within the eon Proterozoic and the only period in the era Mesoproterozoic . It follows the period of columbium and in turn is superseded by the period of cryogenium . The rodinium lasted 930 million years and fills the period from 1780 million years BP to 850 million years BP. It replaces the earlier Statherium , Calymmium , Ectasium , Stenium and Tonium .

designation

The Rodinium, English Rodinian , was derived from the supercontinent Rodinia , which accreted BP between 1300 and 900 million years ago. Rodinia in turn comes from the Russian Родить, rodítj , meaning to give birth or from Родина, ródina , which means motherland, homeland .

Redefinition of the Precambrian Periods

In the course of moving away from period boundaries determined purely by radiometry, the GSSP principle should now be applied as far as possible in the Precambrian, according to Gradstein et al. (2012) . The periods are thus defined on the basis of significant geological events and no longer on arbitrary, radiometric ages.

Definition of the rodinium

Possible reconstruction of Rodinia

The rodinium begins with the first appearance of sulphidic , reducing, marine deposits around 1780 million years BP. A GSSP has not yet been established for the lower bound, but it could be defined with the first appearance of acritars or the first huge sulphide deposits. There is also no GSSP for the upper limit of the rodinium at 850 million years BP, but this could be characterized by the first occurrence of metazoa or by δ 13 C or strontium anomalies.

meaning

Despite the disintegration of the supercontinent Columbia and the subsequent formation of Rodinia in the period 1300 to 900 million years BP, the extremely long, almost one billion years long period of the Rodinian is characterized by a pronounced stability of the essential, biologically relevant isotope systems (for example, the δ 13 C-values ​​in carbonates only slightly around 0 ‰).

The ribbon ores , which were only to reappear to a limited extent around 800 million years BP, disappeared again in it. Significantly, no more glaciations can be recorded in the long course of the rodinium . Other outstanding characteristics of this period (ie of the entire Mesoproterozoic) are sulphidic, reducing deep waters and a gradual diversification of the eukaryotes .

In the earth's atmosphere , the oxygen concentrations continued to rise slowly and steadily (up to 8 to 15% of today's value), but the carbon dioxide partial pressures fell, recognizable by the absence of massive siderite deposits from 1800 million years BP. The methane concentrations probably remained high during the Rodinian and warmed the continents of that time as a thin haze. It is possible that laughing gas (N 2 O) also played the role of a greenhouse gas at the time.

The rise in oxygen gave rise to two new types of ore deposits :

In the case of the world's oceans, Canfield proposes a stratification for the duration of the rodinium (so-called Canfield Ocean ), with an oxygen-rich surface layer and Euxinian , hydrogen-sulphide-rich deep waters. The Canfield model is based on observations such as low sulfate concentrations in seawater (5 to 15% of today's value), sulfide-containing, anoxic deep waters and the formation of massive sulfide deposits. However, the relatively simple Canfield model is not generally accepted, but much more complicated models with lateral and vertical gradients are also being discussed.

The transition from the iron-enriched, oxygen-undersaturated oceans of the Paleoproterozoic to sulphide-containing seas of the Rodinian can be explained on the one hand by the complete precipitation of the available iron, on the other hand by increased oxidative weathering on the continents. As a result of increased erosion activity, sulphates have now been washed into the oceans, which microbes have reduced to sulphides.

Biological evolution

The evolution of living beings experienced a significant diversification of the eukaryotes during the rodinium. The oldest eukaryotic acritars come from the approximately 1800 million year old Changzhougou Formation in the People's Republic of China . Also in China, around 1700 million years old, multicellular organisms were discovered in the Tuanshanzi Formation and Haines (1997) described sedimentary traces in 1750 million year old rocks of northern Australia , which were produced by algae threads .

Grypania spiralis , the oldest known eukaryote, dates back to 2100 million years BP. It still occurs in India, China, and the United States between 1600 and 1450 million years BP. This extremely long distribution time of Grypania was interpreted as evolutionary stagnation, which was supposedly caused by Euxinian deep waters. The low availability of molybdenum , iron and nitrogen is said to have made nitrogen fixation difficult for eukaryotes.

However, macroscopic and microfossil evidence suggests that eukaryotes began to diversify between 1500 and 1400 million years BP. Around 1200 million years BP, in the fossil record, besides eukaryotes, fungal organisms and even microbes can be found on the mainland - which clearly indicates increased oxygen concentrations. In addition, with Bangiomorpha pubescens , a red alga , a sexually reproducing multicellular cell appears for the first time .

Other examples of macroscopic fossils are the so-called pearl necklaces (English string of beads ) encountered from 1500 to 1400 million years BP at several sites. They are likely to be primitive seaweed with anchoring (Metaphyta). Around 1500 million years BP, simple acritarches also appear in the fossil record, which are replaced by much more complex forms between 1200 and 1000 million years BP, which can also be detected on the mainland. The first green algae and heterotrophic eukaryotes develop before the cryogenium has frozen over. Despite the spread of eukaryotes during the rodinium, the evolution-inhibiting effect of the sulphidic Canfield Ocean should not be underestimated.

Geodynamic development

The 1250 to 700/650 million year old Grand Canyon Supergroup on the Colorado River , dipping slightly to the right

The supercontinent Columbia entered a rift phase with the beginning of the Rodinian and began to break apart from 1600 million years BP. This decay process occurs in the sediments of the Belt-Purcell Supergroup on the western edge of Laurentia , the Chhattisgarh Supergroup on the Mahanadi and the Godavari Supergroup on the Godavari in eastern India , the Telemark Supergroup of the Baltic Shield , the Riphean Aulakogen on the southeastern edge of Siberia , the Kalahari Copper Belt on the northwestern edge of the Kalahari Craton and the Zhaertai Bayan Obo Belt on the northern edge of the North China Craton .

The collapse of Columbia was accompanied by widespread, anorogenic magmatism , which, between 1600 and 1300 million years BP , gave rise to the so-called AMCG sequences ( anorthosite - mangerite - charnockite - granite ) in Laurentia, Baltica , Amazonia and northern China . The decay process ended between 1300 and 1200 million years BP, as the intrusion of mafic gang swarms suggests ( Mackenzie gang swarm around 1270 million years BP, Sudbury gang swarm around 1240 million years BP).

Parallel to the collapse of Columbia, accretions went hand in hand, which for example extended the southeastern edge of Laurentia through the Yavapai mountain formation (1800 to 1690 million years BP) and the Mazatzal mountain formation (1710 to 1620 million years BP). In Australia / Antarctica , the Mawson continent was formed around 1600 million years BP .

stratigraphy

Significant sedimentary basins and geological formations
The flat sandstones of the Torridon Group, Torridonian Supergroup , form the horns of the Beinn Alligin

Geodynamics

Igneous accretion belts

Orogenesis

The effects of the Laxfordian on the Lewisian basement, road outcrop near Laxford (Scotland). Even the intrusive pegmatites were deformed and boudinated.

Individual evidence

  1. ^ Felix M. Gradstein et al .: On the Geologic Time Scale . In: Newsletters on Stratigraphy . tape 45/2 , 2012, p. 171-188 .
  2. ^ Li, ZX et al .: Assembly, configuration and break-up history of Rodinia: a synthesis . In: Precambrian Research . tape 160 , 2008, p. 179-210 .
  3. ↑ Des Marais, DJ et al .: Carbon isotope evidence for the stepwise oxidation of the Proterozoic environment . In: Nature . tape 359 , 1992, pp. 605-609 .
  4. ↑ Ohmoto, H. et al .: Evidence from massive siderite beds for a CO 2 rich atmosphere before ~ ​​1.8 billion years ago . In: Nature . tape 429 , 2004, p. 395-399 .
  5. ↑ Kasting, JF: Methane and climate during the Precambrian era . In: Precambrian Research . tape 137 , 2005, pp. 119-129 .
  6. ↑ Buick, R .: Did the Proterozoic 'Canfield Ocean' cause a laughing gas greenhouse? In: Geobiology . tape 5 , 2007, p. 97-100 .
  7. ↑ Jefferson, CW et al .: Unconformity-associated uranium deposits of the Athabasca Basin, Saskatchewan and Alberta . In: Geological Association of Canada, Special Publication . tape 5 , 2007, p. 273-305 .
  8. ↑ Pirajno, F .: Hydrothermal Mineral Systems . Springer, Berlin 2009, p. 1250 .
  9. ↑ Kah, LC et al .: Low marine sulfate and protracted oxygenation of the Proterozoic biosphere . In: Nature . tape 431 , 2004, p. 834-838 .
  10. ^ Arnold, GL et al: Molybdenum isotope evidence for widespread anoxia in Mid-Proterozoic oceans . In: Science . tape 304 , 2004, p. 87-90 .
  11. ↑ Pufahl, PK et al .: Does the Paleoproterozoic Animikie Basin record the sulfidic ocean transition? In: Geology . tape 38 , 2010, p. 659-662 .
  12. ↑ Lamb, DM et al .: Evidence for eukaryotic diversification in the ~ 1800 million-year-old Changzhougou Formation, North China . In: Precambrian Research . tape 173 , 2009, pp. 93-104 .
  13. ^ Zhu, S. and Chen, H .: Megascopic multicellular organisms from the 1700-million-year-old Tuanshanzi Formation in the Jixian area, North China . In: Science . tape 270 , 1995, pp. 620-622 .
  14. ↑ Haines, PW: Tool marks from around 1750, northern Australia: evidence for large drifting algal filaments? In: Geology . tape 25 , 1997, pp. 235-238 .
  15. ↑ Sharma, M. and Shukla, Y .: Taxonomy and affinity of Early Mesoproterozoic megascopic helically coiled and related fossils from the Rohtas Formation, the Vindhyan Supergroup, India . In: Precambrian Research . tape 173 , 2009, pp. 105-122 .
  16. ↑ Du, R. et al.: Discovery of megafossils in the Gaoyushang Formation of the Changchenian System, Jixian . In: Acta Geological Sinica . tape 2 , 1986, p. 115-120 .
  17. ↑ Walter, MR et al .: Megascopic algae 1300 million years old from the Belt Supergroup, Montana: a reinterpretation of Walcott's Helminthoidischniter . In: Journal of Paleontology . tape 50 , 1976, p. 872-881 .
  18. ↑ Glass, JB et al.: Coevolution of metal availability and nitrogen assimilation in Cyanobacteria and algae . In: Geobiology . tape 7 , 2009, p. 100-123 .
  19. ↑ Parnell, J. et al.: Early oxygenation of the terrestrial environment during the Mesoproterozoic . In: Nature . tape 468 , 2010, p. 290-293 .
  20. ↑ Nicholas J. Butterfield: Bangiomorpha pubescens n. Gen., N. Sp .: implications for the evolution of sex, multicellularity, and the Mesoproterozoic / Neoproterozoic radiation of eukaryotes . In: Paleobiology . tape 26 (3) . Jacksonville NY 2000, p. 386-404 , doi : 10.1666 / 0094-8373 (2000) 026 <0386: BPNGNS> 2.0.CO; 2 .
  21. ↑ Martin, DM: Depositional environment and taphonomy of the 'strings of beads': Mesoproterozoic multicellular fossils in the Bangemall Supergroup, Western Australia . In: Australian Journal of Earth Sciences . tape 51 , 2004, p. 555-561 .
  22. ↑ Knauth, LP and Kennedy, MJ: The late Precambrian greening of the Earth . In: Nature . tape 460 , 2009, pp. 728-732 .
  23. ↑ Porter, SM: The fossil record of early eukaryote diversification . In: Paleontological Society Papers . tape 10 , 2004, p. 35-50 .
  24. ↑ Anderson, JL and Morrison, J .: Ilmenite, magnetite and peraluminous Mesoproterozoic anorogenic granites of Laurentia and Baltica . In: Lithos . tape 80 , 2005, pp. 45-60 .
  25. ^ Karlstrom, K. and Bowring, SA: Early Proterozoic assembly of tectonostratigraphic terranes in southwestern North America . In: Journal of Geology . tape 96 , 1988, pp. 561-576 .
  26. ^ Payne, JL et al .: Correlations and reconstruction models for the 2500-1500 Ma evolution of the Mawson Continent . In: Reddy, SM et al. Paleoproterozoic Supercontinents and Global Evolution (Ed.): Geological Society of London, Special Publications . tape 323 , 2009, pp. 319-356 .
  27. ↑ Martin, D. McB. and Thorne, AM: Tectonic setting and basin evolution of the Bangemall Supergroup in the northwestern Capricorn Orogen . In: Precambrian Research . tape 128 , 2004, pp. 385-409 .
  28. ↑ Chaudhuri, AK et al .: Conflicts in stratigraphic classification of the Puranas of the Pranhita-Godavari Valley: review, recommandations and status of the 'Penganga' sequence . In: Geological Society, London, Memoirs . tape 43 , 2014, p. 165-183 .
  29. ↑ Guadagnin, F. et al .: Age constraints on crystal-tuff from the Espinhaço Supergroup - Insight into the Paleoproterozoic to Mesoproterozoic basin cycles of the Congo-São Francisco Craton . In: Gondwana Research . tape 27 , 2015, p. 363-376 .
  30. ↑ Guadagnin, F. and Chemale, F .: Detrital zircon record of the Paleoproterozoic to Mesoproterozoic cratonic basins in the São Francisco Craton . In: Journal of South American Earth Sciences . tape 60 , 2015, p. 104-116 .
  31. ^ Nigel Woodcock and Rob Strachan: Geological History of Britain and Ireland . Blackwell Science Ltd, Oxford 2000, ISBN 0-632-03656-7 .