EVIDENCES OF OSCILLATIONS OF LAND ANT) SEA. 335 



of the Glauconitic, as in the case of the Washita division of the Comanche 

 series, represent a waverins; but progressive shallowing not yet com- 

 pletely interpreted, and it can only be stated that this time was marked 

 by a series of slight oscillations, and that the present seems to be one of 

 elevation. 



All these movements and my estimate of their amplitude are graph- 

 ically represented in the following figure : 



HEOCOMIAN &AULT CtNOMANIAN TURONIAN SLNONPAN tOCtNE. NtOCLNt PLEISTOCtNE 



MONTANA 



FRINITV FaLDEfilCl^SeuRS WASMiTA DAKOTA COLORADO ' GUUCONITIC^ 



Q iT Q 



LAND 



Figure i. — Oncillnlions of Land and Sea shown in Sediments of Red Rir r Region. 



It should be remembered that these movements in the Red river 

 region, as proved by the great extent of the deposits southward to the 

 Rio Grande, were epirogenic, and that they should be recorded, perhaps 

 in varied sediments or erosion surfaces, in the history of the Great plains 

 and eastern Rocky mountain region. 



In the basement Eocene we have still another period when this region 

 was the shoreline Avith corres^oonding littoral deposition, but the details 

 have not been thoroughly investigated. 



The Plateau gravel probably represents the great epoch of Neocene 

 baseleveling, described by INIcGee under the name of the Appomattox 

 and the I^afayette. I believe, from my limited studies, that ultimately 

 the vicissitudes of its physical history will be closely correllated with 

 those of the Llano Estacado. The details of the later Pleistocene history 

 have not been studied. 



In general, it should be remembered that owning to the persistence of 

 the old Ouachita shoreline this Red River region was one in which the 

 average conditions of land and water were near sealevel, while the Rocky 

 mountain region was that portion of our continent which was average 

 upland, and the central Texas region that of great alternations, hence 

 the amplitude of oscillation of each movement was many times greater 

 in the Cordilleran region than in the Red river country. To the west- 

 ward great epirogenic and orographic movements were taking place 

 through thousands of vertical feet of movement to the hundred here. 



