PENNSYLVANIAN. 463 



in certain places faulted. A series of anticlines and synclines have their axes extending 

 northeast-southwest . 



It is not the purpose in this connection to discuss the problem of the cause of the thickening 

 of the various beds of the Muskogee group to the south, or what amounts to the same thing, 

 the thinning of the beds to the north. It has usually been assumed that the change in the 

 thickness is due largely to unconformity by overlap. While in the present state of our knowl- 

 edge, particularly in the absence of complete paleontological evidence, it would be extremely 

 unwise to say that this cause did not obtain, at least in part, still in the light of accumulating 

 evidence it seems very probable that we must look elsewhere for reasons to account for a 

 considerable part of the southern thickening of the beds. 



TULSA GROTTP. 



Area. — This group includes all the rocks lying between the base of the Calvin-Claremore 

 formation and the base of the ledge which in Kansas has been laiown as the Upper Parsons 

 or Coffeyville limestone, but which in a paper by Ohern, now in press, is designated as the 

 Lenapah limestone. The rocks of the group outcrop on the surface as a band, averaging 20 

 miles in width, and extending from the Kansas line south to the region of the Arbuckle Moun- 

 tains. The Lenapah limestone" has not been certainly located south of the North Canadian 

 River, although there is reason for beheving that it will eventually be correlated with a Ume- 

 stone in the upper part of the Holdenville formation, which outcrops not far from the town 

 of Holdenville, in Hughes County, and which probably extends nearly to Ada. The rocks of 

 the Tulsa group occupy all or part of the following counties: Craig, Nowata, Rogers, Tulsa, 

 Wagoner, Okmulgee, Okfuskee, Coal, Hughes, and Pontotoc. 



Stratigraphy. — The rocks of the Tulsa group, as exposed in the northern part of the State, 

 include formations which in Kansas have been described under the names Fort Scott limestone, 

 Labette shales, Pawnee limestone, Bandera shales, Altamont limestone, and Walnut shales. 

 The combined thickness of these rocks at the Kansas hne is about 250 feet; farther south this 

 thickness is much greater. 



The Fort Scott limestone, known to the oil drillers of Kansas and Oklahoma as the Oswego 

 lime, was first described in Kansas, where it consists typically of two hmestone members and 

 an intervening shale member. Ohern, however, finds that in northern Oklahoma a third 

 limestone member comes in below the Fort Scott of Kansas and persists at least as far south as 

 the Arkansas River. For this formation, consisting of three hmestones with two intervening 

 shale beds, each containing coal, in a paper now in press, he is proposing to use the name 

 Claremore. 



The Labette shales, named and described in Kansas, extend from the Kansas line south- 

 ward across Oklahoma, finally, on the disappearance of the higher limestones, coalescing with 

 other shales. The Pawnee and Altamont (Lower Parsons) limestone, which at the Kansas 

 hne are separated by the Bandera shales, come together in southern Nowata County and form 

 a single ledge, the Oologah, the "Big lime" of the drillers. The ledge extends southward, 

 crosses the Arkansas River near Broken Arrow, and disappears in the vicinity of the Concharty 

 Mountains. 



From the Arkansas River south the rocks of the Tulsa group consist of sandstones and 

 shales with an occasional lentil of limestone. In the Coalgate folio Mr. Taff has described 

 the following formations beginning with the Calvin : 



Feet. 



Seminole conglomerate 150 



Holdenville shale 250 



Wewoka formation 700 



Wetumpka shale 120 



Calvin sandstone 200 



If, in ths above section, the Tulsa group includes the Calvin, Wetumpka, and Wewoka 

 formations, and probably 200 feet or more of the Holdenville formation, this would indicate that 



a This formation is not recognizable south of Watora, in Nowata County, Okla. The Dawson coal, however, 

 which occupies practically the same horizon, extends southward beyond Kansas River. — C. D. Smith, comment on 

 manuscript. 



