Lower Triassic: Difference between revisions
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[[File:Chasmatosaurus.jpg|thumb|230px|right|Proterosuchus, an early crocodile-type [[archosaur]]]] |
[[File:Chasmatosaurus.jpg|thumb|230px|right|Proterosuchus, an early crocodile-type [[archosaur]]]] |
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The '''Lower Triassic''' is the first |
The '''Lower Triassic''' is the first [[geology|geological]] [[Epoch (geology)|epoch]] in the [[Triassic]] that began 252.17 [[million]] years ago, and ended at 247 million years ago.<ref>http://www.stratigraphy.org/ICSchart/ChronostratChart2013-01.pdf</ref> Before it was the [[Permian]] It is followed by the [[Middle Triassic]]. |
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It is the oldest epoch of the [[Mesozoic]] [[era]]. These rocks were laid down just after the great [[Permian–Triassic extinction event]]. |
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The Lower Triassic was called the [[Scythian]] stage, which can be found in older literature. In Europe, most of the Lower Triassic is composed of [[sandstone]]. It is a [[lithostratigraphy|lithostratigraphic]] unit of [[continent]]al [[red beds]]. They were formed on land under [[desert]] conditions. |
The Lower Triassic was called the [[Scythian]] stage, which can be found in older literature. In Europe, most of the Lower Triassic is composed of [[sandstone]]. It is a [[lithostratigraphy|lithostratigraphic]] unit of [[continent]]al [[red beds]]. They were formed on land under [[desert]] conditions. |
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Revision as of 01:03, 7 July 2013
The Lower Triassic is the first geological epoch in the Triassic that began 252.17 million years ago, and ended at 247 million years ago.[1] Before it was the Permian It is followed by the Middle Triassic.
It is the oldest epoch of the Mesozoic era. These rocks were laid down just after the great Permian–Triassic extinction event.
The Lower Triassic was called the Scythian stage, which can be found in older literature. In Europe, most of the Lower Triassic is composed of sandstone. It is a lithostratigraphic unit of continental red beds. They were formed on land under desert conditions.
Fauna
The massive extinctions that ended the Paleozoic era caused extreme hardship for the surviving species. Many types of corals, brachiopods, molluscs, echinoderms, and other invertebrates had completely disappeared. The most common hard-shelled marine invertebrates were bivalves, gastropods, ammonites, echinoids, and a few articulate brachiopods. The most common land animal was the herbivorous synapsid Lystrosaurus.
The earliest Triassic faunas lacked biodiversity and were like that throughout the epoch. Recovery on land took 30 million years.[2]
The first ichthyosaurs evolved in this epoch.
The climate during the Lower Triassic (especially in the interior of the supercontinent Pangaea) was generally dry. Deserts were widespread. The poles had a temperate climate. The relatively hot climate of the epoch may have been caused by widespread volcanic eruptions.
References
- ↑ http://www.stratigraphy.org/ICSchart/ChronostratChart2013-01.pdf
- ↑ Sahney S. and Benton M.J. (2008). "Recovery from the most profound mass extinction of all time" (PDF). Proceedings of the Royal Society: Biological. 275 (1636): 759–65. doi:10.1098/rspb.2007.1370. PMC 2596898. PMID 18198148.