CHAPTER V. 



GEOGRAPHY OF NORTH AMERICA AT THE CLOSE OF PERMO- 



CARBONIFEROUS. 



The surface of the United States east of Ozarkia was largely free from an 

 epicontinental sea in the closing period of the Paleozoic. Schuchert,'' in his 

 chart of the submergences, shows a decided retreat of the sea, beginning at 

 the close of the Pottsville and continued until the close of the Upper Permian, 

 when it was at its maximum. In his chart of formations, opposite page 556, 

 he shows Permo- Carboniferous deposits in the bituminous region of Penn- 

 sylvania, the northern Appalachian region, Ohio, Kansas, Iowa, Oklahoma, 

 and central and trans-Pecos Texas. 



Ulrich, in his Revision of the Paleozoic System, page 343, shows an ele- 

 vation at the close of the Pennsylvanian and a withdrawal of the Gulf inva- 

 sion which formed the Permo-Carboniferous limestones of eastern Kansas, 

 Oklahoma, and Nebraska. It is well recognized that in a general way the 

 withdrawal of the seas of upper Pennsylvanian time was by a gradual uplift 

 in the northeast which forced the waters toward the southwest, until the 

 last stand was made in the Texas-Oklahoma-Kansas region within the limits 

 of the Wreford and equivalent limestones.'' On the west this sea was bor- 

 dered by the great flat, generally dry but with many pools, some of large 

 size, crossed or watered by streams and subject to short-lived inundations 

 of ocean water in the southwest (Clear Fork limestones). The border be- 

 tween the sea and the fiat can only be indicated very broadly, and probably 

 never was a stable line; slight changes in level induced wide advances and 

 retreats of the strand lime. Broadly speaking, the border was where the 

 limestones shade into red deposits toward the west, as indicated above (p. 12). 

 On the northern part of the fiat rose the precursors of the Arbuckle Hills, 

 and farther to the west those of the Wichita Mountains, at that time masses 

 of considerable magnitude. 



Gordon'' has given the following account of the sedimentation on this 

 flat in Texas, which is equally applicable to the beds in Oklahoma : 



"Conditions of Sedimentation. — The character of the sedimentation and the 

 contents of the strata in the ' Red Beds ' area suggest that the region was a tidal flat 

 or a low, swampy area subject to overflow and adjoining the open area which lay 

 toward the south and west. This view is maintained by Case, who states that 'the 

 whole formation seems to be very clearly the result of deposition, either in the form 

 of a wide delta or in very shallow water.' He adds, further, that ' the remains which 



» Schuchert, Paleogeography of North America, chart of submergences and emergences and map of 

 Lower Permian. 



'■ Girty, Outlines of Geological History, chap, vi, pp. 126, 127. 



"Gordon, U. S. Geological Survey, Water Supply and Irrigation Paper No. 317, pp. 26, 27, 1913. 

 88 



