ulrich: major causes of osciluations 77 



formed that subsequently lodged a considerable embayment of 

 the Mazomanie sea. 



But this does not exhaust the known record of diastrophic 

 movements of this time in Wisconsin. Uplifts of the relatively 

 evenly distributed floor of Dresbach sandstone are indicated in 

 many places; and depressions occurred in other localities so that 

 the Franconia lapped over in such places on to the pre-Cambrian 

 rocks. This occurs at Berlin and at Taylors Falls, towns loca- 

 ted on opposite sides of the area covered by the formation. At 

 Osceola, on the other hand, there is a narrow ridge on the sur- 

 face of the Dresbach that completely cuts out the Franconia, 

 though the formation is well developed both to the north and 

 south of Osceola. Finally, we recognize two longer upwarps of 

 the Dresbach floor that extend in a southwesterly direction from 

 the central pre-Cambrian land mass which formed the backbone 

 of the Wisconsin peninsula. These buried ridges divided the 

 Franconia sea into basins sufficiently distinct to show well- 

 marked differences in their respective depositional sequences 

 and faunas. 



But why pile up the evidence, the sameness of which must 

 weary you. Suffice it to say that the phenomena indicating 

 differential vertical displacements of the strandline are every- 

 where about us, and as abundant and well displayed in the areas 

 of Paleozoic rocks as in those of more recent ages. One need but 

 to compare a series of paleogeographic maps which, even despite 

 their admittedly generalized and synthetic nature, yet show — 

 unmistakably and clearly — variations in outlines of successive 

 continental seas that would have been impossible if the land 

 surfaces periodically invaded by them had not been subject to 

 frequent oscillation and warping. 



Physiographers, apparently, have paid little attention to these 

 paleogeographic maps and the discussions of stratigraphic cor- 

 relations that usually accompany them. Perhaps the reason 

 for this oversight lies in the fact that most of them have been 

 made by paleontologists — a kind of geologist who should be seen 

 but not heard on physiographic and diastrophic questions. But, 

 after all, does not the stratigraphical paleontologist deal with a 



