2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 69 



It is not easy to abandon inherited notions, even when it can be 

 proved that they have no foundation in fact. I have found it neces- 

 sary in this study, in order to harmonize relations described in a 

 given locality, to take into account many factors, such as the date 

 at which the description was published, the prevailing belief at the 

 time, and the personality of the author — whether progressive or con- 

 servative ; whether an independent thinker or one fearful lest he stand 

 alone. I have attempted here to keep inherited notions in the back- 

 ground and to carefully distinguish between the facts and their 

 published interpretation. I have attempted to visualize the natural 

 processes by which the observed relations were produced. I have 

 endeavored to follow, step by step, the sequence of events as moun- 

 tains were thrown up in the midst of the sea and have tried mentally 

 to observe the evolution of the mountainous region as it was slowly 

 molded under the forces of erosion, peneplained, base-leveled, and 

 finally again submerged by the sea. I have attempted to follow the 

 processes by which vast quantities of rock waste were transported 

 from highlands to lowlands and spread out uniformly over hundreds 

 of thousands of square miles. In brief, I have attempted to picture 

 the physiographic processes which resulted in the stratigraphic rela- 

 tions exhibited by the sedimentary rocks of Mesozoic age in the 

 Southern Rocky Mountain region. 



One of the main objects of this study is to develop a logical 

 grouping of the sedimentary rocks and to establish a method of 

 correlation which may be applied in certain places where other 

 methods fail. As correlation by physiographic criteria is somewhat 

 unusual, opposition is anticipated. It is probably inevitable that the 

 familiar arguments of established lines of thought will find wider 

 acceptance than those of an untried line. The stratigraphic geologist 

 has become so accustomed to relying on the paleontologist for corre- 

 lations that he is apt to reject without due consideration any sugges- 

 tion which seems to be at variance with that derived from the fossils. 

 Chamberlin * recognized this attitude of mind when, in urging the 

 merits of diastrophism, he said, " New criteria must not .... be 

 judged solely by their concordance with established systems; certain 

 divergences may be but signs of superiority." No claim is made 

 that the investigation here described is a finished one. There are 

 radical differences of opinion on some of the questions discussed 



1 Chamberlin, T. C, Cong. geol. internal. Compte Rendu XII, Ges. Canada, 

 p. 551, 1914. 



