S6 RAYMOND C. MOORE AND FREDERICK B. PLUMMER 



Valley, the Hog Creek shale below, and the Home Creek limestone 

 above. The shale is rather sandy, and especially in the north 

 grades into a thick, cross-bedded sandstone at the top. The lime- 

 stone, or rather the series of thin limestones, at the top of the 

 Caddo Creek, has a thickness of lo to 50 feet and in the extreme 

 northern portion of the outcrop disappears. 



A review of the paleontologic evidence and the stratigraphic 

 relations of the Canyon group leads to the conclusion that this 

 portion of the Texas Pennsylvanian is approximately contem- 

 poraneous with the upper portion of the section described in the 

 Coalgate area'' of southern Oklahoma, that is, Calvin to Holden- 

 ville, and perhaps some of the subjacent beds. This includes the 

 Wewoka formation. Since the horizon of the Calvin has been 

 traced northeastward to the Claremore, and this in turn to the 

 base of the Marmaton formation in Kansas, it appears that surface- 

 mapping checks the paleontological correlation made by Girty^ 

 and the Wewoka formation may be regarded as equivalent to a 

 portion of the Marmaton. The horizon of the Lenapah limestone 

 which belongs in the upper part of the Marmaton formation has 

 also been traced across most of Oklahoma and appears to lie just 

 above the Wewoka. 



CISCO GROUP 



The upper portion of the Texas Pennsylvanian included in the 

 Cisco group is characterized by its more clastic sediments, its thin 

 but persistent limestones, and the presence of coal. It includes 

 all the beds between the Home Creek limestone of the Canyon 

 and the lowermost beds containing Permian fossils. The change 

 in the character of the rocks in passing from the Canyon to the 

 Cisco is evidently the result of a diastrophic movement which made 

 shallow the waters in northern Texas and which brought into them 

 large amounts of coarse sand and gravel, chiefly from the north, for 

 the northern portion of the Cisco is materially thicker and more 

 clastic than the southern portion. The total thickness of the Cisco 

 group is about 700 to 800 feet in the southern Pennsylvanian area 



' J. A. Taff, U.S. Geol. Siirv., Geol. Atlas, Folio 74. 

 2 G. H. Girty, U.S. Geol. Surv., Bull. 544 (1915). 



