The Permian period lasts from approximately 291 to 253 million years ago. During this time the continents were welded together into one giant continent called Pangea. The major salt plains of Oklahoma began to form due to the evaporation of sea waters in the area.
Permian Earth
From the PaleoMap Project
Following the episode of mountain building in the Late Carboniferous (Pensylvanian), a shallow sea covered western Oklahoma during the Permian Period. The mountains were largely worn down, and sand and mud eroded from land in the eastern half of the State were carried by rivers that flowed westward to the sea. The red color of these Permian sandstones and shales comes from red iron-oxide compounds deposited with the sand and mud.
The climate was warm and dry, and thick layers of gypsum and salt were deposited from evaporating sea water. White gypsum now caps many of the hills, buttes, and escarpments in western Oklahoma, and the stone is extensively mined for making wallboard and plasters, and as an additive in cement manufacture. The salt layers underlie most of western Oklahoma, but locally they are dissolved by natural ground-water flow and the resultant brines come to the surface at several salt plains.
During the Permian, insects flourished and in Elmo, Kansas and further south into Oklahoma, evidence of as many as 20 orders have been catalogued from the era. Amphibians also left a fossil record from the Permian and generally clustered around water holes and streams. Amphibian fossils of the Permian were generally quite large. Similarly, the reptiles also left an abundant fossil record from the Permian.
Among the most spectacular reptiles of the Permian was the Pelycosaurs. Varanosaurus and Dimetrodon were particular reptiles that lived in Oklahoma during this period. These animals were not dinosaurs but were early relatives.
The Permian ended with the most severe of all Mass Extinction events; as many as 96% of all species were lost. The effects of the Permian extinction was felt equally on land and in the water. Almost all brachiopods became extinct and have bordered on complete extinction ever since. The ammonoids lost all but one family. Trilobites saw their last days on earth at the end of the Permian. On land, fully 75% of all amphibians families and 80% of all reptile families became extinct. In addition, many plant forms went extinct as well.
To date, there are no solid explanations for the mass extinction that brought about the end of the Permian.
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