J. C. Branner — Extension of the Appalachians. 357 



Art. XXXIX. — The former Extension of the Appalachians 

 across Mississippi, Louisiana, and Texas / by John C. 

 Branner. 



Introductory. 



Several years ago I stated that the old Appalachian land 

 area crossed what is now the lower Mississippi Valley from 

 northern Alabama to the pre Cambrian area northwest of 

 Austin, Texas.* I have not published the evidence that seems 

 to support this theory, partly because the work I was doing in 

 the State of Arkansas was constantly adding new facts to the 

 information already in hand. The recent publication by Dr. 

 Henry S. Williams of his paper on the Southern Devonianf 

 induces me to give the results of my observations in connec- 

 tion with this subject in the hope that they may help toward 

 the solution of the interesting problem he discusses, and 

 toward the collection of data concerning the ancient physical 

 geography of the southern states. 



The Cretaceous embay ment. 



Orographic changes, probably dating about the close of the 

 Jurassic, lowered a large area in Mississippi, Louisiana, Texas 

 and southern Arkansas, admitting the sea across the former 

 land as far north as southern Illinois. This embayment and 

 its subsequent history are described by Hilgard,^ and hardly 

 call for detailed description or discussion here. Lower Cre- 

 taceous rocks in Arkansas, Indian Territory, Texas, Alabama 

 and Mississippi rest unconformably upon the upturned edges 

 of Coal Measures rocks. These Cretaceous beds cross Arkansas 

 from southwest to northeast, and cross Alabama and Missis- 

 sippi from southeast to northwest, and Tennessee from south 

 to north. These facts are enough to show that this embayment 

 took place at or about the beginning of Cretaceous time, and 

 that it was caused by a depression in the region over which 

 these sediments are spread. The present paper will deal prin- 

 cipally with the extent of this depression. 



Evidence^ Character and Extent of the Southwestern Appalachian 



Depression. 



The extent and character of the depression that admitted the 

 Cretaceous sea across the Paleozoic rocks of Arkansas, Texas, 



* Geol. Sur. of Arkansas, Ann. Rep. for 1890, vol. iii, 213; Proc. Bost. Soc. 

 Nat. Hist., xxvi, 477. 



f This Journal, May, 1897, pp. 393-403. 



% Geol. History of the Gulf of Mexico, by E. W. Hilgard, this Journal, vol. cii, 

 391-404; Proc. A. A. A. S., xx, 222-236 ; Smithsonian Contributions, No. 248. 



