- Permian is also an alternative name for the Permic languages
The Permian is a geologic period that extends from about 280 to 248 million years before the present (mya). As with most older geologic periods, the strata that define the Permian are well identified, but the exact date of the period's start is uncertain by a few million years. The end of the period is marked by a major extinction event that is more tightly dated. The Permian is named from the extensive exposures in the region around the city of Perm in Russia. The Permian follows the Carboniferous (Pennsylvanian in North America) and is followed by the Triassic. Permian exposures consist largely of continental redbeds and shallow water marine exposures.
The Permian is usually broken into lower (early) and upper (late) subdivisions. The faunal stages from youngest to oldest are:
- Changxingian/Lopingian/Djulfian/Ochoan/Dewey Lake (Zechstein)
- Wujiapingian/Lopingian/Dorashamian/Ochoan/Longtanian/Rustler/Salado/Castile (Zechstein)
- Capitanian/Guadelupian/Kazanian (Zechstein)
- Wordian/Guadelupian/Kazanian (Zechstein)
- Roadian/Ufimian/Guadelupian (Zechstein)
- Kungurian/Irenian/Filippovian/Leonard (Rotliegendes)
- Artinskian/Baigendzinian/Aktastinian (Rotliegendes)
- Sakmarian/Sterlitamakian/Tastubian/Leonard/Wolfcamp (Rotliegendes)
- Asselian/Krumaian/Uskalikian/Surenian/Wolfcamp (Rotliegendes)
Sea levels in the Permian remained generally low, and near-shore environments were limited by the collection of almost all major landmasses into a single continent -- Pangea. One continent, even a very large one, has less shoreline than six to eight smaller ones. This could have in part caused the widespread extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms.
Permian-Triassic extinction event
The Permian ended with the most extensive extinction event recorded in paleontology: the Permian-Triassic extinction event. 90% to 95% of marine species became extinct, as well as 70% of all terrestrial organisms. There is very modest evidence that the extinction could have been caused by climate changes due to impact by a large bolide. There is also significant evidence that massive flood basalts from magma output contributed to environmental stress leading to mass extinction. The reduced coastal habitat and highly increased aridity probably also contributed.
Trilobites, which had thrived since Cambrian times, finally became extinct before the end of the Permian.
Terrestrial life in the Permian included diverse plants, arthropods, amphibians and reptiles. These latter were mostly synapsids (Pelycosaurs and Therapsids). Towards the very end of the Permain the first archosaurs appear (Proterosuchid thecodonts); during the following, Triassic, period these would evolve into more advanced types, and eventually dinosaurs. Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. Fossilized shells of two kinds of invertebrates are widely used to identify Permian strata and correlate them between sites: fusulinids , a kind of shelled amoeba-like protist that is one of the foraminiferans, and ammonoids, shelled cephalopods that are distant relatives of the modern nautilus.
During the Permian, all the Earth's major land masses except portions of East Asia were collected into a single supercontinent known as Pangea. Pangea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean ("Panthalassa", the "universal sea"). Large continental landmasses create climates with extreme variations of heat and cold ("continental climate") and monsoon conditions with highly seasonal rainfall patterns. Deserts seem to have been widespread on Pangea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores. The first modern trees (conifers, ginkgos and cycads) appeared in the Permian.
Three general areas are especially noted for their Permian deposits: the Ural Mountains (where Perm itself is located), China, and the southwest of North America, where the Permian Basin in the U.S. state of Texas is so named because it has one of the thickest deposits of Permian rocks in the world.
Last updated: 06-02-2005 14:00:36