224 ASHLEY — GEOLOGY OF AE KANSAS. [Mavis, 



layers. Owing to minor folds some of the higher strata are ex- 

 posed in this belt. 



2. To the north the higher beds are successively exposed, ending 

 in the upper or productive Coal Measures near the Arkansas river. 



3. To the south the higher strata are exposed for a short distance, 

 but still further south they are covered by Cretaceous rocks. 



4. The Cretaceous and the overlying Tertiary beds extending 

 southward to the State line. 



The strata we are to consider are those mentioned under the 

 third head of the preceding paragraph : the beds deposited between 

 the Silurian and the end of Carboniferous times, and exposed south 

 of the Silurian exposures of southwestern Arkansas, and north of the 

 Cretaceous area. 



The northern limit of this area is a line starting from Social 

 Hill in 4 S., 18 W., and touching Point Cedar, Rock Creek and 

 Langley, then passing through the centre of township, 4 S., range 

 30 W., to Potter. West of Potter these beds swing around the end 

 of the Silurian anticlinal nose and unite with the beds of the 

 same age and character lying north of the Silurian area. On the 

 east the boundary nearly follows the Ouachita river to the mouth of 

 the Caddo river, thence on the south the line follows the Caddo 

 and up Big DeGray creek, then turns south to Hollywood, then 

 west, and follows a very irregular line, touching Clear Springs, 

 Antoine, Royston, Nathan, Muddy Fork, Atwood, Ultima Thule, 

 and so on into the Indian Territory. 



n. Salient Features of the Region. 



A General Description of the Area. — The region under con- 

 sideration is a rocky, hilly country stretching along the south side 

 of the Ouachita mountains. It varies in width from fifteen to 

 thirty miles ; the part lying in Arkansas is about ninety miles long. 

 It is for the most part densely wooded and thinly settled. The 

 surface is broken into a great number of valleys and ridges having 

 an east and west trend, with a {q'n narrow and usually rugged north 

 and south valleys. Few, if any, of these ridges are more than three 

 hundred feet in height. 



The most common type is a ridge or table land having a steep north 

 face, while the south side slopes away gently. A few are narrow, 

 sharp ridges with uneven crests and steep flanks on both north and 

 south sides. All others may be taken as variations of these two 



