H. T. Hill — North American Cretaceous History. 283 



sketch of the principal historical events recorded in their for- 

 mations, and also a preliminary section which approximately 

 outlines the Cretaceons history of the United States east of 

 the Sierras. 



Continental limitations at the beginning of the Cretaceous. 



Early in these investigations it became apparent that the 

 marine sedimentation of both divisions of the Cretaceous sec- 

 tion had been limited on the north by an older continental 

 shore line which must be defined before the subsequent his- 

 tory could be traced. The present remnant of this ancient 

 shore line in the whole Neozoic history of the region was 

 found to be a more or less connected orographic system, with 

 a score of local names, which extends from the Ouachita 

 river in the vicinity of Malvern and Hot Springs, Arkansas, 

 almost due west through Indian Territory into the Panhandle 

 of Texas. The remnant of this mountain system consists 

 of some of the highest and most sharply defined ridges above 

 the surrounding plain in America, as in western Arkansas, 

 south of the Arkansas river, or again of strings of small knobs, 

 as in the Potato hills of Indian Territory ; but whatever their 

 name or shape, it is every where evident that they are the now 

 greatly degraded remnants of a series of nearly vertical folds 

 which once constituted a continuous mountain system which 

 was elevated at the close of the Paleozoic. 



The former extent of this system can not be stated, for its 

 present eastern termination was truncated abruptly and ob- 

 scured by late Cretaceous and Tertiary deposits of the Missis- 

 sippi embayment, while its western continuation is buried 

 beneath Permian, Cretaceous and Quaternary sediments of the 

 Texas Panhandle and obliterated by the later uplifts of the 

 Rocky Mountain regions. The exact stratigraphic relations of 

 this system to the Paleozoic area of Central Texas have not 

 been determined, except that the latter's eastern margin pre- 

 sents a succession of sediments similar to those of the former, 

 and its western border records an early Mesozoic history not 

 seen along its eastern.* It is also evident that it was com- 

 pletely covered by sediments during the two great subsidences 

 in Cretaceous time", while the eastern half at least of the Ar- 

 kansas Indian Territory system remained above sea-level until 

 present time. 



* The western border of this Central Paleozoic region, which presents an en- 

 tirely different system of strata from the eastern, will be treated in another 

 paper. 



