DIASTROPHISM AS BASIS OF CORRELATION 305 



must first test our criterion, for we are not as yet quite sure that 

 contemporaneity of glaciation is inferred on reliable grounds. The 

 shallow-water life of the diastrophic stages is driven into narrow 

 border tracts and into local embayments, and is thus forced into 

 special adaptations and into narrowly provincial aspects. 



(4) The early stages of quiescence and of base-leveling, with 

 advancing seas, are peculiarly fruitful in biological criteria, for they 

 are marked by re-expansions of the narrowly provincial shallow- 

 water faunas of the previous stages. The progressive development 

 of these provincial faunas and their successive unions with the faunas 

 of neighboring provinces, as these come to coalesce by means of 

 the progressive sea-advances, form one of the most fascinating 

 chapters in life evolution, and give some of the most delicate of criteria 

 for correlation. 



This rough outline is quite too meager duly to set forth the criteria 

 of correlation connected with the stages of general diastrophism. It 

 rather suggests them than sets them forth. 



It remains to consider the precedence among themselves of the 

 three factors, diastrophism, deposition, and life development. 



We are accustomed to look to the life record as our chief means 

 of correlation. Its very high utility is quite beyond discussion. 

 Thoughtful students, however, recognize that the paleontological 

 record is based, in an essential way, on stratigraphy and that it is 

 corrected and authenticated by the precise place the life is found to 

 occupy in the stratigraphical succession. Stratigraphy and paleon- 

 tology thus go hand in hand, each sanctioning the other. Diastro- 

 phism lies hack oj both and furnishes the conditions on which they 

 depend. The relationship is not reciprocal in any radical sense. 

 The life does not, in any appreciable way, affect diastrophism. 

 Deposition has been thought to be related to mountain-folding. 

 Erosion in one area and deposition in another has been assigned as 

 an initial agency in deformation. While some influence of this kind 

 may be conceded, I think it is rather a localizing influence than a 

 fundamental one. If wrinkling must take place from other causes, 

 quite possibly previous erosion here and deposition yonder may 

 localize the wrinkling. But that is quite apart from fundamentally 

 causing the wrinkling. Reasons are growing yearly in cogency why 



