Lomagundi Jatuli isotope excursion

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The Lomagundi-Jatuli isotope excursion represents the most significant, positive anomaly of the δ 13 C – values in the entire history of the earth . It occurred in the Paleoproterozoic during the interval 2220 to 2100 million years BP ( Rhyacium ). It allows conclusions to be drawn about profound changes in the redox behavior of the world's oceans.

Etymology and first description

The Lomagundi-Jatuli isotope excursion , in English as the Lomagundi-Jatuli isotope event (abbreviated LJIE) or mostly just as the Lomagundi excursion or Lomagundi event (abbreviated as LE), was named after the Lomagundi Group in Zimbabwe , in which they are first detected could.

The first detailed description of the isotope excursion was made in 1975 by Schidlowski, among others, in the course of their investigation of Precambrian carbonate formations . The actual discovery, however, goes back to 1968 and is due to Galimov and others, which they were able to prove in the Jatulium Karelia .

introduction

The transition from the Archean to the Paleoproterozoic was a time of great global environmental changes. The most significant of these changes was undoubtedly the great oxygenation event (Engl. Great oxidation event or GOE) that came into play in about from 2.45 billion years BP and had fully deployed from 2350 to 2280 million years BP. In connection with the increasing oxygen concentrations, the Huronian Ice Age occurred , which took place in three phases (Ramsey Lake - 2420 to 2405, Bruce - 2370 to 2360 and Gowganda - 2315 to 2305 million years BP).

In the course of the Paleoproterozoic, the sedimentary events were more and more shaped by organic, carbon-rich deposits , which are already to be found very frequently from 2000 million years BP. Phosphorites formed for the first time from 2200 million years BP . In addition, abundant calcium sulphates of marine origin (also from 2200 million years BP) and the ribbon ores typical for this period were formed .

With the breaking of the neoarchean formed Super continent Superia (or Kenorland ) from 2.2 billion years BP and the so-called crustal age gap (or Global Magmatic Shutdown magmatic), a 250-million-year period of stagnation (2450-2200 million a BP ), and extremely slowed plate tectonics , significant geodynamic changes had also occurred.

proof

The Lomagundi-Jatuli isotope excursion could be verified practically worldwide , apart from the type locality in Zimbabwe and the first site in Karelia, with the exception of Antarctica . The following occurrences are documented:

Characterization of the isotope excursion

Curve of the Lomagundi-Jatuli isotope excursion

Martin et al. (2013a) determined a maximum duration for the positive δ 13 C isotope excursion of 249 ± 9 million years (interval 2306 to 2057 million years BP) and a minimum duration of 128 ± 9 million years (interval 2221 to 2093 million years BP). The positive deflection is likely to have occurred in one go, but the authors do not rule out several deflections in future fine resolution.

From the end of the Archean period up to around 2300 million years BP, the δ 13 C values ​​are fairly constant at 0 ‰ VPDB ( Vienna Belemnite Standard ), only to rise gradually and then suddenly. The rapid rise begins at around 2,225 million years BP. The absolute maximum value of around 14 ‰ VPDB was reached around 2175 million years BP. The curve drops again after passing through the maximum, but the drop is less steep than the increase. By 2020 million years BP, 0 ‰ VPDB was reached again, which was maintained until the end of the Paleoproterozoic. Note: the curve has a spread of about 3 ‰ VPDB.

For a better understanding of the course of the curve, a few comparative values ​​that underline the exceptional character of the Lomagundi-Jatuli isotope excursion:

Explanation

The development of the δ13C values ​​over time is directly linked to the oxygen content of the earth's atmosphere. By reducing non-organic carbon (such as in carbon dioxide ) to organic carbon compounds (generally multiples of CH 2 O), oxygen is released. The photosynthetic fixation of carbon shows a preference for the lighter 12 C isotope, which is enriched compared to 13 C. This explains e.g. B. the very low values ​​for organic carbon.

If large amounts of organic carbon are withdrawn from the ecosystem through sedimentation and subsequent sealing in geological formations, not only does the oxygen content in the sea and the atmosphere rise, but at the same time the δ13C values ​​of the undissolved, non-organic carbon begin to rise as well as increasing sedimentary carbonates.

The enormous increase in the δ13C values ​​during the Lomagundi-Jatuli excursion can therefore be explained causally by the increased oxygen production, which was triggered by the rapid growth of cyanobacteria during the previous Great Oxygen Catastrophe . At the same time organic carbon had in significant quantities in the form of, for example, black shales (Engl. Black shales ) that occur more frequently towards the end of the isotopic excursion for the first time, have been precipitated.

Individual evidence

  1. ↑ a b M. Schidlowski, R. Eichmann, CE Junge: Precambrian sedimentary carbonates: carbon and oxygen isotope chemistry and implications for the terrestrial oxygen budget . In: Precambrian Res. Band 2 , 1975, p. 1-69 .
  2. ↑ EM Galimov, NG Kuznetsova, VS Prokhorov: On the problem of the Earth's ancient atmosphere composition in connection with results of isotope analysis of carbon from the Precambrian carbonates . In: Geochemistry . tape 11 , 1968, p. 1376–1381 (Russian, with English summary).
  3. ^ Q. Guo, inter alia: Reconstructing Earth's surface oxidation across the Archean-Proterozoic transition . In: Geology . tape 37 , 2009, p. 399-402 .
  4. ↑ A. Bekker, HD and Holland: Oxygen overshoot and recovery during the early Paleoproterozoic . In: Earth Planet. Sci. Lett. tape 317-318 , 2012, pp. 295-304 .
  5. ^ Papineau, D .: Global biogeochemical changes at both ends of the Proterozoic: insights from Phosphorites . In: Astrobiology . tape 10 , 2010, p. 165-181 .
  6. ↑ KC Condie, DJ Des Marais, D. Abbot: Precambrian superplumes and supercontinents: a record in black shales, carbon isotopes, and paleoclimates? In: Precambrian Research . tape 106 , 2001, pp. 239-260 .
  7. ↑ KC Condie, C. O'Neill, RC Aster: Evidence and implications for a widespread magmatic shutdown for 250 My on Earth . In: Earth and Planetary Science Letters . tape 282 , 2009, pp. 294-298 .
  8. ↑ VA Melezhik, AE Fallick: A widespread positive δ13C carb anomaly at around 2.33–2.06 Ga on the Fennoscandian Shield: a paradox? In: Terra Nova . tape 8 , 1996, pp. 141-157 .
  9. ↑ JA Karhu: Paleoproterozoic evolution of the carbon isotope ratios of sedimentary carbonates in the Fennoscandian Shield . In: Geological Survey of Finland Bulleti . tape 371 , 1993, pp. 1-87 .
  10. ^ P. Salminen,: Carbon isotope records of sedimentary carbonate rocks in the Pechenga Belt, NW Russia: implications for the Precambrian carbon cycle . University of Helsinki (PhD thesis), 2014.
  11. ↑ AJ Baker, AE Fallick: Evidence from Lewisian limestones for isotopically heavy carbon fiber in two-thousand-million-year-old sea water . In: Nature . tape 337 , 1989, pp. 352-354 .
  12. ↑ UN Zagnitko, IP Lugovaya: Isotope Geochemistry of Carbonate and Banded Iron Formations of the Ukrainian Shield . In: Naukova Dumka . Kiev 1989 (Russian).
  13. ^ A. Bekker, J. A Karhu, KA Eriksson, AJ Kaufman: Chemostratigraphy of Paleoproteroizoic carbonate successions of the Wyoming Craton: tectonic forcing of biogeochemical change? In: Precambrian Research . tape 120 , 2003, p. 279-325 .
  14. ↑ A. Bekker, AN Sial, JA Karhu, VP Ferreira, CM Noce, AJ Kaufman, AW Romano, MM Pimentel: Chemostratigraphy of carbonates from the Minas Supergroup, Quadrilátero Ferrífero (Iron Quadrangle), Brazil: a stratigraphic record of Early Proterozoic atmospheric , biogeochemical and climatic change . In: American Journal of Science . tape 303 , 2003, p. 865-904 .
  15. ↑ A. Bekker, AJ Kaufman, JA Karhu, NJ Beukes, QD Swart, LL Coetzee, KA Eriksson: Chemostratigraphy of the Paleoproterozoic Duitschland Formation, South Africa: implications for coupled climate change and carbon cycling . In: American Journal of Science . tape 301 , 2001, pp. 261-285 .
  16. ↑ JF Lindsay, MD Brasier: Did global tectonics drive early biosphere evolution? Carbon isotope record from 2.6 to 1.9 Ga carbonates of Western Australian basins . In: Precambrian Research . tape 114 , 2002, pp. 1-34 .
  17. ↑ B. Sreenivas, S. Das Sharma, B. Kumar, DJ Patil, AB Roy, R. Srinivasan: Positive δ13C excursion in carbonate and organic fractions from the Paleoproterozoic Aravalli Supergroup, Northwestern India . In: Precambrian Research . tape 106 , 2001, pp. 277-290 .
  18. ↑ H. Tang, Y. Chen, G. Wu, Y. Lai: Paleoproterozoic positive δ13Ccarb excursion in the northeastern Sino-Korean craton: evidence of the Lomagundi Event . In: Gondwana Research . tape 19 , 2011, p. 471-481 .
  19. ^ AP Martin, DJ Condon, AR Prave, A. Lepland: A review of temporal constraints for the Paleoproterozoic large, positive carbonate carbon isotope excursion (the Lomagundi-Jatuli Event) . In: Earth Science Reviews . tape 127 , 2013, p. 242-261 .
  20. ↑ TF Anderson, MA Arthur: Stable isotopes of oxygen and carbon and their application to sedimentologic and paleoenvironmental problems . In: MA Arthur, TF Anderson, IR Kaplan, J. Veizer, LS Land (Eds.): Stable Isotopes in Sedimentary Geology . 1983.
  21. ↑ JA Karhu, HD Holland: Carbon isotopes and the rise of atmospheric oxygen . In: Geology . tape 24 , 1996, pp. 867-879 .