THE PERMIAN PERIOD 181 



Distribution and Character of the Rocks 



General Distribution. — Compared with the preceding Pal- 

 eozoic systems, the Permian rocks have a rather limited distribu- 

 tion. There are small areas in Nova Scotia and New Brunswick; 

 a small area in Pennsylvania, Ohio, and West Virginia; large areas 

 in Texas, Oklahoma, Kansas, Colorado, Nebraska, and Iowa; 

 smaller areas in South Dakota and Wyoming; and some rather 

 poorly known areas in New Mexico, Utah, northern Arizona, 

 northern California, and the Pacific border of Alaska. All of these 

 surface exposures are within the areas represented on the map 

 (Fig. Ill) either as occupied by marine waters or receiving con- 

 tinental deposits. 



In the western United States the Permian strata are consider- 

 ably more extensive than their surface distribution because they 

 are concealed under Mesozoic or Cenozoic rocks over large areas. 

 Also there is some reason to think that the Permian strata for- 

 merly extended over much of the Great Basin region, but have 

 been removed by erosion, leaving much Pennsylvanian or Missis- 

 sippian rock now at the surface. In the eastern United States, 

 however, the one small area in the northern Appalachian district 

 comprises all of the Permian except possibly some in the lower 

 Mississippi Valley where Mesozoic and later rocks effectually con- 

 ceal the older rocks. 



Character of the Rocks. — The Permian strata (Dunkard 

 series) in the small area of the northern Appalachian district are 

 sandstones and shales, together with some limestone and coal beds. 

 They are in every way much like the Coal Measures just below. 



In Kansas the Permian rocks are divisible into two rather dis- 

 tinct series, the lower or Big Blue series of shales and limestones 

 being largely marine, while the upper or Cimarron series of sand- 

 stones, shales, dolomitic limestones, and gypsum are mostly not 

 truly marine and they are characterized by a prevailing red color. 



The Texas Permian strata are chiefly red beds of mostly non- 

 marine origin and divisible into three series as shown above. Red 

 clays, limestones, and sandstones constitute the two lower series, 

 while limestone, salt, and gypsum chiefly make up the upper series. 



Marine Permian strata of considerable thickness have been 

 reported from the Wasatch Mountains of Utah, and from northern 

 California. 



