INSTABILITY IN STILVTIGRAPHIC CLASSIFICATION 289 



PART I. INTRODUCTORY CHAPTERS 



Present Instability in stratigraphic Classification 



0AUSE8 



The obvious unrest of the present day in matters pertaining to geologic 

 chronology should be ascribed, I think, chiefly to the fact that strati- 

 graphic knowledge has progressed far beyond the stage of prevailing 

 schemes of classification. These schemes do not fit the known condi- 

 tions. Not only were they founded on a mere fraction of the mass of 

 data now available, but also the criteria used were frequently misinter- 

 preted. Besides, the pioneers in this branch of geology had no concep- 

 tion of the complicated and variable conditions for which we now have 

 to account; hence their practice has resulted in an inconsistent and in- 

 congruous arrangement of stratigraphic units. 



But the weakest feature in these classifications is that their original 

 framers availed themselves almost exclusively of a single kind of evi- 

 dence, namely, that afforded by the fossil faunas and floras. If the fos- 

 sils of geographically separated formations agreed in general aspect and 

 composition, and especially if the percentage of the identified or sup- 

 posed vicarious species was large, then the stratigraphic units were corre- 

 lated. The possibility of locally surviving species or faunas, or of local 

 variations in development, was not considered. 



But these early practices were merely the extreme swing of the pendu- 

 lum. The great success attending the use of fossils in correlation when 

 compared with the results accomplished under the wholly incompetent 

 methods previously employed not only placed stratigraphic geology on a 

 firm basis, but induced a blind and unquestioning confidence in paleon- 

 tologic evidence. The word "blind" is used advisedly," because an un- 

 prejudiced analysis of correlations by fossils in the fifty years preceding 

 the past decade shows beyond deijial they were made in practical disregard 

 of factors vitally concerned in tlie production of local facies of faunas. 



Under the circumstances it is not surprising that the efficiency of fossil 

 evidence began to be questioned ; that good philosophers began to discuss 

 "shifting of faunas," to use expressions like this, "it required a long 

 time for the Olenellus fauna to encircle the globe" ; or for another to say 

 "the very fact that geographically separated faunas are the same proves 

 they are not contemporaneous." Presently others, chafing under the 

 yoke of the "Paleontological autocrat," were suggesting classes of evi- 

 dence and modes of correlation that might entirely supersede that based 

 on fossils. Dual nomenclatures are proposed, new principles of correla- 

 tion are suggested, and a symposium of correlation is arranged. It is 



