370 Branner — Former Extension of the Appalachians 



sea lay along the eastern base of the Rocky Mountains, for 

 while marine Coal Measures fossils are not common in the 

 eastern part of the Coal Measures area, in Illinois and Arkansas 

 they are much more plentiful, and in rocks of the same age 

 along the foot of the Rocky Mountains they are still more 

 abundant. 



Resume. 



I. The Ouachita anticline is the structural equivalent of 

 the Cincinnati-Nashville arch ; this fold continues westward 

 through the Arbuckle mountains in Indian Territory and to 

 the Wichita mountains in southern Oklahoma Territory. 



II. The Coal Measures drainage of the Illinois-Indiana-Ken- 

 tucky basin flowed westward through the Arkansas valley into 

 a Carboniferous mediterranean sea. 



III. The drainage of the Coal Measures region south of the 

 Ouachita anticline flowed westward and entered this sea north 

 of the Texas pre-Cambrian area. 



IV. The drainage of both the Arkansas and Texas Car- 

 boniferous areas was reversed about the end of Jurassic times, 

 when orographic movements over southeast Arkansas, eastern 

 Texas, Louisiana, and Mississippi submerged the former exten- 

 sion of the Appalachian watershed and admitted the early 

 Cretaceous sea across the Paleozoic land as far north as southern 

 Illinois. 



V. This depression was not a deep one (Hilgard)* and did 

 not all occur at one time, for there have been subsequent dis- 

 turbances of a more or less similar nature in the same region. 



VI. The evidences of these depressions are : 



1. The reversed drainage of the Arkansas valley. 



2. The reversed drainage over the Carboniferous area of cen- 

 tral Texas. 



3. The submerged eastern end of the Ouachita uplift. 



4. The eastward slope of the peneplain of the Ouachita region. 



5. The direction of the faults and folds near the eastern expo- 

 sure of the Lower Coal Measures in Arkansas. 



6. The great fault through Texas near the Tertiary border, hav- 

 ing a downthrow of 1000 to 1500 feet on the south and east sides. 



7. Eruptive rocks accompanying the Texas fault and the Ter- 

 tiary border through that state and Arkansas to the Arkansas 

 river. 



8. Hot springs near the same line. 



9. Faults in Alabama with a downthrow of 10,000 feet or 

 more on the northwest side. 



10. The thickness of the Cretaceous and Tertiary sediments 

 over the depressed area: from 4,000 to 10,000 feet. 



* This Journal, 1871, vol. cii, p. 394. 



