226 ASHLEY — GEOLOGY OF ARKANSAS. [May 13, 



Much of the land is too broken for cultivation except for some 

 hillside crop like grapes, which are said to do well here. 



While most of the soil is sandy and not very rich, there is much 

 good land along the streams, particularly in the eastern part. In 

 the western part of the region most of the available land is on the 

 divides. 



Conclusions. — A summary of the conclusions deduced from a 

 study of the features above touched upon can best be given as a 

 history of geologic events in the region. 



The Periods of Deposition. — The deposition of the rocks took 

 place before the end of the Carboniferous age, and as the rocks are 

 of both Silurian and Carboniferous ages, it must have been during 

 these times that these sediments were laid down. 



The Lower Silurian beds are the novaculites, with the accompany- 

 ing shales and sandstones. The Carboniferous strata are sandstones 

 and shales, with which occur a little grit, novaculite and some 

 other rocks. No nonconformity has been found between the two 

 sets of beds. The Silurian beds are believed to underlie the sand- 

 stones of the Carboniferous over all of the region, though they have 

 been recognized at only one place. 



The original thickness of the Carboniferous strata is not known, 

 nor is it known whether the whole or only a part of the Carboni- 

 ferous series was laid down over this territory. The beds remain- 

 ing are thought to belong mostly to the Lower Coal Measures. 

 The only fossils found are a few fragments of plants. No satisfac- 

 tory columnar section has been obtained of the beds, but their 

 thickness cannot be less than four or five thousand feet. 



Period of Folding. — At the end of the Carboniferous age, or pos- 

 sibly before it, the beds of sediment in southwestern Arkansas and 

 the adjacent portion of the Indian Territory began to yield to an 

 apparently horizontal pressure. Gradually the great Ouachita up- 

 lift rose, and the upper beds began to fold. This continued until 

 the upper beds were folded closely and frequently even over- 

 thrown ; in fact, in this area the overthrown folds or overturns are 

 the most common kind of fold, and testify to the intensity of the 

 folding action. 



This folding took place very slowly, so slowly that erosion may 

 Iiave almost kept pace with the uplifting beds. Besides the two 

 kinds of anticlines, the normal anticline and the overturned anti- 

 cline, the region is full of faults and crushed and broken structure ; 



