234 ASHLEY — GEOLOGY OF AEKANSAS. [May IS, 



Superposition of the Beds. 



Mr. Griswold divides the Silurian strata into two series ; the 

 novaculite series, and the beds below the novaculites. The beds 

 below the novaculites he estimates to be 1300 feet in thickness, as 

 far down as exposed. They consist of gray, black and yellow 

 shales at the bottom, cherty blue limestones next above, then mas- 

 sive quartzose sandstones, limestones, and shales. 



From several columnar sections the novaculite series appears to 

 vary greatly in different localities. He gives, however, a general- 

 ized section, in which the order from the bottom upward is : 

 Silicious shales, 200 feet; shale, 300 feet; novaculite, 250 feet; 

 shale, 100 feet; novaculite, 100 feet; novaculite with silicious 

 shale at bottom, 250 feet ; novaculite breccia or conglomerate, a 

 thin layer. 



The variation in these layers may be judged by an examination 

 of Mr. Griswold' s sections.^ Thus, as an example, the upper layer 

 of novaculite in the Boss Allen Creek section is 500 feet thick, 

 while in the South Fork of the Caddo section it is only 60 feet 

 thick. 



Stratification of the Carboniferous Beds. — No satisfactory col- 

 umnar sections of the Carboniferous beds were obtained. 



Outside of the immediate channels or banks of streams, rock 

 exposures are rare, and when found are seldom extensive enough 

 to give more than the dip, and the rock exposures in the stream are 

 not usually more than a few yards long. Now and then a continu- 

 ous exposure is found for several hundred feet, and in a few cases 

 longer exposures are found ; but usually between the long exposures 

 there are so many stretches concealed, in which may be folds, or 

 faults, or other unknown factors, that one cannot be sure of the 

 structure. Had the beds been such as to permit identification and 

 correlation, doubtless satisfactory sections could have been made. 

 On Plate I are given the best general sections obtained. 



Plate /, Section I. — This section was obtained on the Rolling 

 Fork of the Little river. In 8 S., 32 W., the lower part of section 

 II, is a perpendicular bluff on the east bank of the Rolling Fork 

 known as the ''Buzzards' Roost." The dip at this point is about 

 12°, S. 18° E. Continuing up stream, sandstone is met with in 

 bluffs and in the stream bottom almost continuously, dipping from 



1 Geol. Surv. of Ark., An, Rep. for 1890, Vol. iii, PI. iii. 



