Karoo Ice Age

The Karoo Ice Age (360 to 260 million years ago) was the second great ice age of the Phanerozoic . It is named after the glacial deposits found in the Karoo in South Africa , which were the first clear evidence of this ice age.

One also speaks of the permocarbon or permocarbon glaciation , as it shaped the Carboniferous and Permian .

background

The tectonic amalgamation of the continents Euramerica (later with the Ural Orogeny , to Laurasia ) and Gondwana to Pangea in the Variscan Orogeny created a large continental land mass in the Antarctic region, and the disappearance of the Rheic Ocean or the Iapetus interrupted the warm ocean currents in the Panthalassa and in the Tethys Sea , which resulted in progressive cooling of the summer and accumulated snow. This in turn led to the growth of glaciers in the mountains, which then spread out over the highlands and formed an ice sheet that covered a relatively large part of Gondwana.

At least two major periods of glaciation have been discovered:

• The first glaciation occurs in the Mississippium (358.9 to 323.2 million years ago): The ice sheets spread from a core in what is now southern Africa and South America .
• The second glaciation period falls in the Pennsylvania (323.2 to 298.9 million years ago); The ice sheets spread from a core in what is now Australia and India .

The extent of glaciation in Antarctica is not exactly known because of the existing ice sheet.

Consequences of the Karoo Ice Age

Scratches formed by glaciers during the Karoo Ice Age in Witmarsum Colony, Paraná , Brazil

The effects of the Karoo Ice Age begin with the Dwyka Ice Age around 300 to 280 million years ago. At that time, today's Namibia was in the area of ​​the South Pole . The inland ice masses can be documented by Tillite (solidified moraines) and the sandstones and shale formed from sediments. In the dry season that followed, the Dwyka area was buried by debris known as the Etjo or Ecca . This phase ended with the breakup of Gondwana and the subsequent drift of Africa from South America around 132 million years ago. The resulting Etendeka flood basalts, up to two kilometers thick, preserved the previously existing Dwyka relief. Weathering and erosion reappear the underlying land surface.

During the Karoo Ice Age, there was an increased concentration of oxygen in the atmosphere, which stimulated the plants in the warmer areas to increase their metabolism. This resulted in increased growth in the Carbon Age and the development of large vertebrates or the arthropod Arthropleura or insects such as the giant dragonfly Meganeura .

literature

• RA Berner: Atmospheric oxygen over Phanerozoic time . In: Proc. Natl. Acad. Sci. USA . 96, No. 20, 1999, pp. 10955-7. bibcode : 1999PNAS ... 9610955B . doi : 10.1073 / pnas.96.20.10955 . PMID 10500106 . PMC 34224 (free full text).
• DJ Beerling, RA Berner: Impact of a Permo-Carboniferous high O2 event on the terrestrial carbon cycle . In: Proc. Natl. Acad. Sci. USA . 97, No. 23, 2000, pp. 12428-32. bibcode : 2000PNAS ... 9712428B . doi : 10.1073 / pnas.220280097 . PMID 11050154 . PMC 18779 (free full text).
• Sylvi Haldorsen, Victor von Brunn, Rodney Maud, Edward D. Truter: A Weichselian deglaciation model applied to the Early Permian glaciation in the northeast Karoo Basin, South Africa. In: Journal of Quaternary Science. (September 2001) pp. 583-593, ISSN  0267-8179 .
• CR Fielding, Tracy D. Frank, John L. Isbell: Resolving the late Paleozoic ice age in time and space. In: Special papers. 441. Geological Society of America, Boulder (Colorado) 2008, ISBN 978-0-813-72441-6 .

Web links

• Geology and plate tectonic basic structure - Karoo series on geo.uni-tuebingen.de

Individual evidence

1. ↑ Alien forests ( Memento of the original from March 3, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on planeterde.de, accessed on November 22, 2013. 
2. ↑ Geology and basic plate tectonic structure - Karoo sequence ( Memento of the original from January 6, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. at geo.uni-tuebingen.de, accessed on November 22, 2013. 
3. ↑ DJ Beerling, RA Berner: Impact of a Permo-Carboniferous high O2 event on the terrestrial carbon cycle . In: PNAS . 97, No. 23, 2000, pp. 12428-32. bibcode : 2000PNAS ... 9712428B . doi : 10.1073 / pnas.220280097 . PMID 11050154 . PMC 18779 (free full text).