1897.] 



ASHLEY — GEOLOGY OF ARKANSAS. 



249 



This section has been compiled from observa- 

 tions by members of the survey.^ 



It shows a monocline on the north, a syncline 

 in the centre, an anticline south of that, and a 

 nonconformity at the southern limit. 



The gradual change from practically horizontal 

 strata on the north to highly folded on the south 

 is also shown. 



At the north Silurian strata are exposed, but on 

 going south these gradually sink beneath Carbon- 

 iferous deposits, to appear again in the great anti- 

 cline of the Ouachita uplift. On disappearing 

 again they continue but a short distance below the 

 surface, until they and the overlying Carboniferous 

 beds are covered by the gently dipping Cretaceous 

 strata. 



The section is given to show the relation of the 

 area under discussion to the general section of 

 western Arkansas. The line on which the section 

 is made crosses the Ouachita uplift not far from 

 its western nose, so that the Silurian outcrop is 

 very small compared with what it would be on a 

 north-south line further east, and likewise the Car- 

 boniferous outcrop south of the Silurian would be 

 narrower in a section further east. 



Historical. 



None of the early writers on the geology of 

 Arkansas seem to have made any attempt to work 

 out the structure of the Ouachita uplift, or of the 

 region immediately south of it. 



Comsiock} — The first attempt to give system to 

 the folds was made by Dr. Theo. B. Comstock 



i\Vinslow, «' Geotectonic and Physiographic Geology of 

 Western Arkansas," Bulletin Geological Society of Ainer- 

 ica. Vol. ii, pp. 225-242, Fig. I ; Geol. Surv. of Ark., 

 Rep. for 1 89 1, Vol. iv, sections; Geol. Surv. of Ark., 

 Rep. for 1890, Vol. iii, section on Mt. Ida sheet; Gecl. 

 Surv. of Ark., Rep. for 1888, Vol. ii, sections p. 126. 



•^ Geol. Surv. of Ark., Rep. for 1888, Vol. i, pp. 130- 

 166. 



