462 INDEX TO THE STEATIGEAPHY OF NORTH AMERICA. 



the north by the Kansas line, and on the northeast by the areas occupied by Mississippian rocks. 

 On the east the Arkansas Hne is the boundary. The Choctaw fault, the Cretaceous overlap in 

 Atoka County, and the Arbuckle Mountains demark the southern limit. It includes all or part 

 of the following counties in Oklahoma: Ottawa, Craig, Mayes, Rogers, Wagoner, Cherokee, 

 Okmulgee, Muskogee, Sequoyah, Le Flore, Haskell, Mcintosh, Okfuskee, Hughes, Latimer, 

 Pittsburg, Coal, Pontotoc, and Atoka. 



Stratigraphy. — Near the Kansas line, in which State the name Cherokee shales has been 

 applied to the rocks of the group, the approximate thickness of the strata is 450 feet and con- 

 sists largely of shales, with local beds of sandstone and limestone and several thin beds of coal. 

 The f oUowiag section from Pryor Creek to Claremore made by Messrs. Ohern and Wolf will give 

 a fairly comprehensive idea of the stratigraphy at that place. 



Section from Pryor Creek to Claremore. 



Feet. 



14. Shale with a few interbedded sandstones 135 



13. Massive medium-grained sandstone 17 



12. Shaly sandstone 3 



11. Argillaceous, heavily bedded fossiliferous limestone 2J 



10. Bluish shale 35 



9. Carbonaceous shale Capped by 6 inches of ferruginous siliceous limestone 3 



8. Gray fine-grained sandstone 7 



7. Arenaceous shale 70 



6. Alternating shales and sandstones 70 



5. Argillaceous fossiliferous limestone 8 



4. Massive medium-grained sandstone 37 



3. Shaly sandstone 8 



2. Massive medium-grained sandstone 14 



1. Bluish shale, weathering to light yellow, and a few interstratified sandstones 550 



960 

 In the Muskogee folio Mr. Taff describes two formations, the Boggy and the Winslow, the 

 latter being the equivalent of the Hartshorne, McAlester, and Savanna formations as exposed 

 in the coal fields farther south. The formations above the Boggy have not been described in 

 Muskogee, Okmulgee, and Mcintosh counties. 



The stratigraphy of the southern part of the Muskogee group is better understood than 

 that of any other part of the Pennsylvanian series in Oklahoma. Numerous reports and folios 

 bearing upon the subject, chiefly from the pen of Mr. Taff, whose work in the region continued 

 almost without interruption from 1895 to 1908, have given us a very comprehensive idea of the 

 stratigraphy, structure, and economic resources of the coal fields of the State. The general 

 sequence of the formations with their approximate thickness as shown in Coal and Hughes 

 counties is here given, the oldest below: 



Feet. 



Calvin sandstones 200 



Senora formation 500 



Stuart shale ' 250 



Thurman sandstone 200 



Boggy shale 2,000 



Savanna sandstone 1,200 



McAlester shales 2,000 



Hartshorne sandstone 200 



Atoka formation 3,000 



9,550 



This entire series of strata is coal bearing. In Arkansas beds of considerable thickness 

 occur in the Atoka formation, but in Oklahoma these beds are usually thin and inconspicuous. 

 The McAlester formation contains four beds of workable coal and a number which may event- 

 ually be developed. The Savanna contains at least three and, the Boggy formation two workable 

 beds. Several occur in the higher formations of the series, particularly one in the upper part 

 of the Senora which is mined at Henryetta, Schulter, and Morris. In the southeastern part of 

 the area occupied by rocks of the Muskogee group the strata have been extensively folded and 



