Silurian
From Wikipedia, the free encyclopedia.
This period is part of thePaleozoic era. |
Permian |
Carboniferous |
Devonian |
Silurian |
Ordovician |
Cambrian |
- Alternate use: The Silurians, a reptillian race from the series "Doctor Who".
The Silurian system was first described by Sir Roderick Murchison in the 1830s based on rocks in South Wales. It is named for a Welsh Celtic tribe -- the Silures. The series quickly came to overlap Adam Sedgwick's Cambrian sequence. Lapworth eventually resolved the conflict by defining a new Ordovician system including the contended beds.
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2 Silurian paleogeography 3 Silurian fauna |
Silurian subdivisions
The Silurian is usually broken into Lower and Upper subdivisions, however some workers do use a Lower/Middle/Upper breakdown. The Faunal stages from youngest to oldest are:
- no stage defined? (Upper-Pridoli)
- Cayugan (Upper- Ludlow)
- Ludfordian (Upper- Ludlow)
- Gorstian (Upper- Ludlow)
- Homerian/Lockportian (Middle-Wenlock)
- Sheinwoodian/Tonawandan (Middle-Wenlock)
- Telychian/Ontarian (Lower-Llandovery)
- Aeronian/Alexandrian (Lower-Llandovery)
- Rhuddanian/Alexandrian (Lower-Llandovery)
Silurian paleogeography
During the Silurian, Gondwana remained in high Southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late Ordovician. The other continents drifted together near the equator starting the formation of a second supercontinent known as Laurasia.
Silurian fauna
Life was abundant in the Silurian. Silurian beds are oil and gas producers in some areas. Extensive beds of Silurian hematite -- an iron ore -- in Eastern North America were important to the colonial economy.
The Silurian was a time of high sea levels in Eastern North America and Europe. Primitive multicelled land plants are found from the Silurian. A few arthropods seem to have invaded the land during the Silurian. Fish reached considerable diversity and developed movable jaws. A diverse fauna of Sea Scorpions -- some of them several meters in length -- graces the Silurian of North America. Brachiopods, bryozoa, mollusks, etc were abundant and diverse