PENNSYLVANIAN. 461 



PROPOSED SOLUTION. 



The authors are convinced that the problem of the future division and correlation of the 

 various beds may be greatly simplified by dividing all the rocks in the region into a few general 

 groups, the limits of which may be demarked by certain conspicuous ledges of limestone and 

 sandstone which extend southward from the Kansas line. After studying the region in con- 

 siderable detail, it has been found that there are at least four of these ledges of sufficient impor- 

 tance and linear extent along the line of outcrop to serve as adequate group markers, which 

 groups must,, of course, be confirmed by paleontological evidence. Beginning on the east, these 

 ledges are as follows : 



1. The Claremore formation, the approximate equivalent of the Fort Scott limestone of 

 Kansas, which is correlated with the Calvin sandstone in the Coalgate folio. 



2. The Lenapah limestone, which lies at the approximate horizon of the Upper Parsons 

 or Coffeyvfile limestone of Kansas. 



3. The Pawhuska formation, which is believed to be the equivalent of the Deer Creek and 

 Hartford limestones of Kansas. 



4. The Wreford limestone, which, south of the Cimarron River, gives way to the Payne 

 sandstone. 



From the study of the map it will be seen that these four formations trend approximately 

 parallel northeast and southwest, from the Kansas line toward the region of the Arbuckle Moun- 

 tains. The southern extension of none of them has been definitely located, but it is believed that 

 accurate .field studies will fix the position of each formation. 



PROPOSED GROUPS. 



It is therefore proposed to demark the limits of four general groups of the Pennsylvanian 

 rocks of eastern Oklahoma as follows : 



1. The Muskogee group, including all the rocks from the base of the Pennsylvanian series 

 to the base of the Claremore formation. The name proposed is that of Muskogee County, which 

 lies near the center of the area occupied by the group. 



2. The Tulsa group, including everything from the base of the Claremore formation to the 

 base of the Lenapah limestone. The name is from Tulsa County, in the eastern part of which 

 the rocks of the group are well exposed. 



3. The Sapulpa group, including the rocks between the base of the Lenapah Hmestone and 

 the base of the Pawhuska formation. The name is from Sapulpa, the county seat of Creek 

 County. 



4. The Ralston group, including everything from the base of the Pawhuska to the base of 

 the Wreford, which has usually been considered the base of the Permian. The name here 

 proposed is from the town of Ralston, in northern Pawnee County. 



In proposing these groups the authors do not wish to be understood as attempting to fix 

 definitely the nomenclature of the region. The purpose is merely to provide a comprehensive 

 yet simple scheme of classification which may be followed in future mapping. The classification 

 is made entirely upon stratigraphic and lithologic data. 



DESCRIPTION OF GROUPS. 

 MUSKOGEE GROUP. 



Area. — The Muskogee group includes a series of rocks, chiefly sandstones and shales, extend- 

 ing from an unconformity at the top of the Mississippian series on the east to the base of the 

 Claremore formation" and its approximate southern equivalent, the Calvin sandstone, on the 

 west. In the northern part of the State it includes the approximate area occupied by the south- 

 ern continuation of the Cherokee shales of Kansas; in the southern extension it includes the 

 great coal region of Oklahoma. The area included in this group in Oklahoma is bounded on 



"This formation includes the Fort Scott limestone of Kansas and some of the upper part of the Cherokee shale. 

 At the south boundary of the Claremore quadrangle as much as 100 feet of the Cherokee is included.— C. D, Smith, 

 comment on manuscript. 



