642 ELIOT BLACKWELDER 



Permian) red beds. Thus it is the conclusion of Taff' ''that the 

 Arbuckle uphf t [ = crumpHng] began near the middle and culminated 

 near the close of Pennsylvanian time, previous to the deposition of 

 the red beds." 



The folds are sharply compressed and cut by overthrusts and 

 other faults as in the Appalachians, but there are no contempo- 

 raneous igneous intrusions and the rocks were not much meta- 

 morphosed. In Oklahoma, the Arkansan system of folds trends 

 east by south, but the strike becomes more nearly east and west in 

 Arkansas. Extensions of the system in the line of strike are 

 unknown, because both to the west and to the east the folded beds 

 are concealed by overlapping horizontal strata of later age. The 

 same is true to the south. South westward in the Llano^ district of 

 central Texas, early Pennsylvanian strata are the youngest 

 involved in the very mild folding and faulting which the stratified 

 rocks now show. Their deformation may perhaps be related to the 

 Arkansan disturbance. North of the Arkansas River the Car- 

 boniferous strata still lie almost horizontal, and in Kansas there is 

 not so much as a disconformity between the early and later Penn- 

 sylvanian strata. In the Ozark region of Missouri and northern 

 Arkansas the very gentle flexures and normal faults may possibly 

 be referable to this epoch, but as yet the evidence is of little weight. 

 SKght deformation of the Mississippian and older strata along the 

 Mississippi River in Illinois, Iowa, and Missouri, and the making 

 of the LaSalle anticline of Illinois seem to have in large measure 

 preceded the Pennsylvanian, and if so, are not to be correlated 

 with the Arkansan orogeny. The disturbance seems too slight to 

 include, in the present list, as a distinct orogeny. 



The folding of the Ouachita beds has been referred by Dana and 

 others to the Appalachian revolution. However, unless published 

 correlations are seriously in error we must conclude that the 

 Ouachita folds had been formed and truncated before the deposition 

 of the latest Pennsylvanian sediments, whereas the Appalachian 

 folds were not begun until after the early Permian strata had been 



' J. A. Taff , " Geology of the Arbuckle and Wichita Mountains," U.S. Geol. Survey, 

 Prof. Paper 31, p. 80. 



^ Sidney Paige, U.S. Geol. Survey, Llano Folio, No. iSj, Texas. 



