Permian period


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Permian period

Permian period (pûrˈmēən) [from Perm, Russia], sixth and last period of the Paleozoic era (see Geologic Timescale, table) from 250 to 290 million years ago.

Historical Geology of the Period

The Lower Permian

During the Permian period, changes in the earth's surface that had begun in the preceding Carboniferous period reached a climax. At the close of the Carboniferous, large areas of E North America were dry land. In the Lower Permian, sandy shales, sandstones, and thin limestones of the Dunkard formation (formerly called the Upper Barren measures) were deposited in the remaining submerged areas of West Virginia, Pennsylvania, and Ohio, but the continued rising of the land soon put an end to deposition. The Dunkard is the last Paleozoic formation of the E United States. More extensive deposits were formed in the West. Parts of Texas, Oklahoma, Kansas, and Nebraska were covered by an arm of the sea or possibly by one or more salt lakes or lagoons, now represented by masses of salt or gypsum in layers separated and overlaid by red beds. There are important Permian salt mines at Hutchinson and Lyons in Kansas and gypsum mines in Oklahoma, Texas, and Kansas. The longest marine submergence of the Lower Permian in North America was in W Texas and SE New Mexico, where there is a system of marine limestones and sandstones 4,000 to 6,000 ft (1,200–1,800 m) thick. The Cordilleran region was also submerged; here marine beds are more common toward the west, and land sediments, especially red beds, toward the east. The red beds are generally considered to be indicative of increasingly arid conditions in Permian times.

In Europe, the Lower Permian, or Rotliegendes [red layers], was marked principally by erosion from the Paleozoic Alps of the Carboniferous into the low-lying land to the north; the formations are chiefly shale and sandstone, with some conglomerate and breccia. Red is a prominent color for the beds. The Pangaea supercontinent formed from an aggregation of all continents at this time.

The Permian and late Carboniferous of the Southern Hemisphere were radically different from those of the Northern Hemisphere. Australia, S Africa, and South America experienced a series of glacial periods, as is shown by the presence of tillite and of conspicuous striations of the underlying rock formations. This condition prevailed also in India. Paleozoic glaciation in North America is suggested by the Squantum tillite near Boston, Mass. This glaciation and the aridity of which the red beds seem to be the result are the two most strongly marked characteristics of the Permian period.

The Upper Permian

In the Upper Permian practically all of North America was above sea level, and the continent was larger than at present. Toward the close of the Upper Permian the greatest earth disturbance of the Paleozoic era thrust up the Appalachian Mts. In Europe, the Upper Permian was a period of more extensive marine invasion; the Zechstein formation is predominantly limestone, though it includes rich deposits of copper, salt, gypsum, and potash. The Upper Permian beds of Germany were long the chief source of the world's potash.

Evolution of Plant and Animal Life

Many marine animals became extinct during the Permian, but there was at the same time an evolution to more modern types, a marked change in the insects, and a notable increase in numbers and varieties of reptiles mainly because of the continental changes. Among plants, Lepidodendron and Sigillaria became rare, but ferns and conifers persisted. The widely distributed “seed fern,” Glossopteris, which was apparently successful in resisting glacial conditions, was the most conspicuous development in the Permian flora. The presence of Glossopteris in South America, Antarctica, Australia, and S Africa is a strong argument favoring the interconnection of these land masses in a large supercontinent during Permian time. The end of the Permian is marked in the fossil record by the Great Dying, the most devastating mass extinction known.
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References in periodicals archive ?
These petrified forests of the Permian Period are important because of their location and altitude.
But in the Permian period, Earth's single ocean may have been an immense stagnant sea, thanks to a long cycle of beach-towel weather 250 million years ago.
Among the significant conclusions of the new paper will be that the extinctions of most bryozoans at the end of the Permian Period did not occur overnight as the result of some catastrophe, but over an 8- to 10-million-year period.
They are believed to have lived between 1 to 2 million years ago during the Permian period when all the continents were connected.
The book starts in the Permian period, beginning 299 million years ago, and concludes long after the dinosaurs' demise, in the Pleistocene with Titanus walleri, a "terror bird" that lived until 1.8 million years ago.
The Chhidru Formation, Western Salt Range, Pakistan represents not only the termination of late Permian period, but also the end of Paleozoic era.
To determine whether eruptions from the Siberian Traps triggered a massive increase in oceanic carbon dioxide, Burgess and Bowring are using similar dating techniques to establish a timescale for the Permian period's volcanic eruptions that are estimated to have covered over five million cubic kilometers.
23 ( ANI ): Researchers have suggested that the mass extinction at the end of the Permian period, about 250 million years ago, was triggered by contemporaneous volcanic eruptions in Siberia.
The cliffs began life as limey mud on the floor of a shallow, warm tropical sea more than 250 million years ago during the Permian period. Frenchman's Bay: Named after a French ship which ran aground in the 17th century.
The biggest of all happened at the end of the Permian period, 245 million years ago, when 96% of all marine species and 75% of land vertebrates perished.