STRATIGRAPHIC CLASSIFICATION DIASTROPHIC CRITERIA 40.1 



It is not my intention to imply that the systemic boundaries can not 

 be drawn in the several continents so as to insure against the possibility 

 of referring contemporaneous beds to the top of, say, the Silurian in 

 Europe, and to the base of the Devonian, system in America. On the 

 contrary, I believe that accuracy in correlation, whether narrow or inter- 

 continental in scope, depends solely on the uniform application of the 

 criteria and principles adopted, and that if our practice is thoroughly 

 consistent we shall Jfinally succeed in discovering physical boundaries 

 that will separate the systems so that none will include beds of ages else- 

 where referred to either the preceding or the succeeding period. This 

 may sound unduly optimistic, but Judging from my own experience in 

 the still young science of stratigraphy it is not so. The greatest diffi- 

 culties lay not in the correlation of sections personally studied ; they 

 arose rather from the continual expansion of the stratigraphic column 

 and the frequent readjustments and changes in classification thereby 

 necessitated. In short, they have been taxonomic rather than objective; 

 and withal never so great as to discourage the hope that where I have 

 failed others may succeed. 



Results of recent methods of correlation. — The feature of advancing 

 knowledge of stratigraphic correlation that more than any othei* is 

 responsible for the expansions of the sedimentary record briefly out- 

 lined on pages 379 to 381 lies in the gradual conviction that instead of 

 stable, slowly growing continents covered with great, long enduring 

 and deep interior seas, the surface of the continents was exceedingly 

 unstable and subject to frequent oscillation and more or less local warp- 

 ing, the seas were correspondingly inconstant, shallow, relatively small, 

 and frequently withdrawn entirely, only to reappear in forms simulating 

 preceding geographic patterns. The effect of this revised conception 

 seems so far-reaching that if proved true it must greatly modify — per- 

 haps revolutionize — stratigraphic geology. Possibly this statement is 

 stronger than is warranted by the evidence. But the facts bearing it out 

 are not only abundant and of varied kinds, but they are repeated over 

 and over again so much that I can not help being convinced of the truth 

 of the principle of oscillating seas and lands. In fact, this principle is 

 at the basis of whatever new philosophy is established or suggested in 

 this paper. 



Not so many years ago it was commonly accepted that extensive migra- 

 tions of the shoreline resulted principally from en masse elevation and 

 subsidence of the continents. Latterly, and more particularly since the 

 publication of Suess's "Antlitz der Erde," the transgressions of the sea 



