1897.J ASHLEY — GEOLOGY OF ARKANSAS. 261 



which resisting decay would indicate the presence of the hard 

 layers beneath. Many of the overturns in the eastern part of the 

 area were worked out in this way. 



To resume, overturns may be suggested or located : (i) by the 

 existence of anticlines to the east or west of a given locality ; (2) by 

 the prevalence over an unusually broad area of high dips in one 

 direction ; (3) by topographic relief; (4) by the exposure in parallel 

 outcrops of deep-seated beds. 



VI. Detailed Structure on the Eastern Sheet. 



The detailed structure will be described under the artificial 

 divisions made by the two map sheets of the area. The two 

 general divisions of the eastern sheet may be studied under : 



T. The Caddo Valley. 



2. The area of drift, the Chalybeate mountain being taken as 

 the northern edge of the area of drift. 



Eastern Portion of Caddo River Valley. 



The Caddo valley may be divided into an east and west portion, 

 the dividing line being in range 22 W. 



As will be explained more fully elsewhere, the topography of the 

 portion of the eastern sheet north of the Chalybeate mountain, 

 while broken up by divides and ridges into minor valleys, is a broad 

 valley, differing in manyVays from the country south of Chalybeate 

 mountain. 



Blakeley Creek Anticline. — The limits of this anticline were not 

 definitely determined, but the ridge produced by it is between 100 

 and 150 feet high and five miles long, running from 4 S., 18 W., 

 section 27, to 4 S., 19 W., section 26, along the south side of 

 Blakeley creek. The ridge is of novaculite, but the novaculite bed 

 is only poorly exposed. The ridge is serrated (as illustrated under 

 Prairie Bayou anticline, Fig. 16), steep on the north side, the south 

 side forming a water-shed to Prairie Bayou. It is highly probable 

 that this anticline is continued further east, connecting with the 

 one a mile and a half north of Social Hill. 



Mijior Anticlines. — Two minor anticlines were found in 4 S., 

 18 W., south half of section 29. 



By minor anticlines is meant those in which the evidence of fold- 

 ing is meagre, or which could not be traced or other evidence of 



