532 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



CORRELATION BY DIASTROPfflG MOVEMENTS 



General discussion of principles. — Diastrophism, the initial cause of 

 physical and organic change, is urged by Chamberlin as the ultimate 

 basis of correlation. The essential features of his conclusion are ably 

 presented by this writer in a recent short paper on the subject^®, and 

 also by Willis^^ who emphasizes certain aspects not definitely stated by 

 the former. Assuming the principle of periodicity of great deformations, 

 both conclude that the baseleveling of the land in the relatively quiescent 

 stages between the periods of active diastrophism "means contempo- 

 raneous filling of the sea basins by transferred matter," and that the 

 resulting advance of the sea "is essentially contemporaneous the world 

 over" (Chamberlin op. cit., page 690). Willis thinks "the eras of inac- 

 tivity, the baselevel eras for the whole world," were very long, and 

 because of "their very great duration, from which their essential con- 

 temporaneity results," they are unfitted "for any except the broadest 

 outline of classification." Further on he adds that these baselevel eras 

 "afforded the best conditions for correlation by the other criteria." Ee- 

 garding periods of active diastrophic movement he says, they ^Tiave been 

 shorter than the eras of baseleveling, and consequently define time 

 divisions, which are more nearly commensurate with those of current 

 geologic standards. They are, however, still long, and their value is in 

 broad fundamental classification." That Willis believes only very crude, 

 generalized, correlations are possible by means of continental and oro- 

 genic movements is evident from the following statement: "Disturbance 

 and quiet, erosion and continuous deposition, unconformity and con- 

 formity, have developed simultaneously in immediately adjacent districts 

 many times" (Willis, op. cit., pages 255, 256). Finally, according to 

 this author, only the occasional world-wide ebbs, resulting from sub- 

 sidences beneath the oceans, would seem to constitute anything like an 

 exact measure of Contemporaneity. 



Chamberlin and Willis have presented the theoretic aspects of the 

 principles of diastrophic correlation in sufficient detail, but, so far as 

 I know, no practical application of the proposition, except in the broad- 

 est and most generalized terms, has been published. Indeed, such appli- 

 cation is no easy matter, the problems being exceedingly complex and 

 quite insolvable except with the aid of the most refined paleontological 

 methods. Chamberlin probably recognizes this fact when he says "if 

 we add the biological element the case is immeasurably strengthened;" 



•* T. C. Chamberlin : Diastrophism the ultimate basis of correlation. Journal Geology, 

 vol. 17, 1909, pp. 685-693. 



■^0 Bailey Willis : Principles of paleogeography. Science, Feb. 18, 1910. 



