Sturtic Ice Age

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The Sturtic Ice Age or Sturtic Ice Age was an ice age of the cryogenium . It was one of at least three major ice ages in the era of the Neoproterozoic . References to this Ice Age were provided, among other things, by the Tillit rock from the South Australian Sturt Valley, which gives it its name . Ice-age deposits from other parts of the world, including northern Australia ( Kimberley region), north-western Canada ( Ogilvie Mountains , Mackenzie Mountains and Victoria Island ), Namibia ( Otavi group ), southern China (Yangtze craton) and Oman ( Huqf group ), are assigned to the Sturtic Ice Age type.

geology

Information about the exact time of the Sturtic Ice Age varies greatly and depends on the determination method used and the location of the investigation. They range from about 760 million years ago to about 640 million years ago. Due to the great temporal differences, the existence of several Sturtic Ice Ages is also discussed. According to current regulations, a Sturtic Ice Age is said to have occurred about 715 million years ago and lasted at least five million years.

The extent of the Sturtic Ice Age is also the subject of scientific discussions. According to the snowball earth hypothesis , it led to practically complete glaciation of the entire earth. The South Australian rocks of Ice Age origin from the Precambrian , whose paleomagnetism suggests a deposit near the equator, are an indication of this. According to other theories, the ice age rock deposits can be traced back to several local glaciations without global glaciation.

Flora and fauna

The Sturtic Ice Age had a significant impact on the development of life on earth. Before the Sturtic Ice Age, the differentiation of eukaryotic life forms began. Micro- and macro fossils prove the existence of Amoebozoen , Rhizarien , red algae , green algae and Chromalveolaten . With the beginning of the Sturtic Ice Age, there was a drastic decline in the number of life on earth. Only a few microfossils date from the time from the beginning of the Sturtic Ice Age to the end of the Cryogenium. The time between the Sturtischen and the subsequent Marino Ice Age is predicted , based on genetic studies, as the time of the first appearance of multicellular animals ( Metazoa ). Molecular traces from this period indicate the appearance of the first sponges .

Individual evidence

  1. ^ Kaufman AJ, Sial AN, Frimmel HE: Neoproterotoic to cambrian paleoclimatic events in southwestern Gondwana . In: Hartwig E. Frimmel; Claudio Gaucher; Alcides N. Sial; Galen P. Halverson (Ed.): Neoproterozoic-Cambrian Tectonics, Global Change and Evolution, Volume 16: A Focus on South Western Gondwana (Developments in Precambrian Geology) . Elsevier Science, Amsterdam 2009, ISBN 0-444-53249-8 , pp. 369-388. .
  2. ^ A b Macdonald FA, Schmitz MD, Crowley JL, et al. : Calibrating the Cryogenian . In: Science . 327, No. 5970, 2010, pp. 1241-1243. doi : 10.1126 / science.1183325 .
  3. ↑ Kendall B, Creaser RA, Selby D: Re-Os geochronology of postglacial black shales in Australia: Constraints on the timing of “Sturtian” glaciation . In: Geology . 34, September 2006, pp. 729-732. doi : 10.1130 / G22775.1 .
  4. ↑ Knoll AH, Javaux EJ, Hewitt D, Cohen P: Eukaryotic organisms in Proterozoic oceans . In: Phil. Trans. R. Soc. B . 361, 2006, pp. 1023-1038. doi : 10.1098 / rstb.2006.1843 .
  5. ↑ Love GD, Grosjean E, Stalvies C, et al. : Fossil steroids record the appearance of Demospongiae during the Cryogenian period . In: Nature . 457, No. 7230, February 2009, pp. 718-21. doi : 10.1038 / nature07673 . PMID 19194449 .