302 ASHLEY — GEOLOGY OF ARKANSAS. [May 13, 



To the northeast of the Caddo are four smaller creeks, Blakely 

 creek, Prairie creek, Bayou Delile, DeRoche creek. Between the 

 Caddo and the Little Missouri are Terre Noir creek and Antoine 

 creek. The still smaller creeks are shown on the maps. As a rule, 

 the tributaries run at right angles to the main streams. Thus, the 

 Caddo runs nearly east, its tributaries nearly all run south, and this 

 same relation can be traced with but few exceptions to the Cossa- 

 tot, which runs south, but has east and west tributaries. 



Going from east to west the general elevation increases more 

 rapidly on the north edge of the maps than on the southern ; con- 

 sequently the difference of elevation between points on the north 

 and south edges of the maps is greater in the western part than in 

 the eastern. 



The effect of this is quite marked, both upon the character of the 

 streams and upon the topography ; this is still further intensified by 

 the direction of the streams in the eastern part, giving them the ad- 

 vantage of the longest side of the slope. Thus the Caddo and 

 other streams in that region may be characterized as a succession of 

 long, deep pools connected by short rapids having only a few inches, 

 fall. Further west the Cossatot and Rolling Fork are, for much 

 of their courses, shallow, rapid streams with but few stretches of 

 quiet water. 



Comparatively speaking all the streams are rapid. The more 

 western streams probably averages between fifteen and twenty- 

 five feet fall to the mile ; the Caddo has a fall of seven or eight 

 feet to the mile. 



In the same way the topography changes from east to west. In 

 the east it consists of broad valleys with many bottoms along the 

 streams. In the west the valleys are narrow, deep and steep-sided. 

 In the Cretaceous area the smaller streams are mostly surface 

 streams not having cut channels of any great depth. This, to a 

 large extent, is also true of the smaller streams of the Caddo valley, 

 though, where their courses compel them to cut across ridges, they 

 become more rapid and have abrupt banks. In the western part, 

 where the tributaries as a rule follow structural lines, they sink their 

 beds rapidly in the shaly strata, producing deep, narrow ravines, and 

 where these are quite numerous, the topography becomes exceed- 

 ingly broken. 



