uIvRich: major causes of oscil,l,ations 67 



often very closely, in parts, with the next preceding or some 

 earlier sea, but in other parts the new shoreline departs radically 

 from the older. 



These movements occurred in Paleozoic ages which, unlike 

 the Pleistocene, have left no record of great ice accumulations. 

 Doubtless even in the Paleozoic there were times of relative 

 frigidity — ^when some of the higher parts of the marginal lands 

 were ice-covered, in some instances attaining locally to glacial 

 conditions. Here and there regular tillites are indicated, nota- 

 bly, as recently brought out by Dr. Edwin Kirk, in the Silurian 

 deposits along the coast of Alaska. Occasionally, too, trans- 

 portation of bulky erratics by heavy shore ice is suggested, as 

 for instance by the late Ordovician Rysedorph hill conglomerate 

 near Albany, N. Y., and the great masses of unworn limestone 

 of Ordovician and Silurian ages found in the early Pennsyl- 

 vanian Caney shale of eastern Oklahoma. But the Paleozoic 

 history of North America so far as known affords no suggestion 

 of icy ages comparable to the Pleistocene period in the amount 

 of water abstracted for the formation of the ice sheets. More- 

 over, by far the majority of the displacements of the strand- 

 line in the continental seas occurred at times and places that 

 give no indication whatever of particularly cool climates. On 

 the contrary, the entombed faunas in the overlapping and inter- 

 fingering marine formations could hardly have lived in the shal- 

 low seas if the climate of the adjacent lands had not been mild. 



With the data in hand I feel warranted in asserting that the 

 level of the Paleozoic continental seas was seldom appreciably 

 affected and certainly never controlled by glaciation. Besides, 

 the apparently irregular, though doubtless rhythmic, shif tings 

 of the strandline almost without exception indicate local differ- 

 ential movement in the continental surface. And these move- 

 ments must have been connected with other more general move- 

 ments, requiring at times partial or complete withdrawal of the 

 waters from the land depressions, at other times permitting 

 readvance in the same or some other newly depressed land basin. 



The varying distribution of marine deposits of successive 

 ages naturally suggests differential upward and downward move- 



