62 NEW YORK STATE MUSEUM 



If these conclusions are correct, the paleogeographic importance of the 

 graptolite shales consists as mentioned before in the fact that they, in con- 

 trast to the majority of the other clastic rocks with their imbedded mollusk 

 faunas, mark the presence of deeper basins of relatively long continuity. 



We will now proceed to show how the view of the long persistence of 

 these deeper basins of the principal graptolite regions falls nicely in line 

 with certain paleogeographic principles enunciated in the last decade. We 

 refer especially to Suess's conception of the relation of the Canadian and 



dorph hill near Albany, and of grit beds; and of the claim advanced by Dale of an uncon- 

 formity between the Beekmantown and Trenton beds by the absence of the Chazy, whi< h 

 assertion in its turn has obviously led to the inference, by Ulrich and Schuchert, of a 

 draining of the Levis basin in Chazy time. 



Professor Dale in his excellent expose of the geological cycles through which the slate 

 belt has passed [1899, p. 298] says of the Lower Cambric sediments: "The frequent alter- 

 nation of fine and coarse sediments, and of these with calcareous ones, and the occurence 

 of conglomerates indicate changing conditions. There was deep and shallow water, quiet 

 water and rapid currents, occasional exposure of the sea bottom to wave action and then 

 its submergence owing to minor oscillations of the earth crust," and states of the Charn- 

 plainic: "The Lower Cambrian sediments are followed by the grits, red and green shales 

 and slates of the Ordovician. The same alternation of coarse and fine sediments con- 

 tinues." We agree with Dale that occasional ridges — minor oscillations that were pre- 

 nuncial of the more general orogenic movement that followed at the end of Champlainic 

 time — were raised at times, causing in part the intercalations of coarser clastic rocks. 

 Similar cases are recorded from the larger geosynclines of Europe, and Haug has pointed 

 out that the first step in the formation of folds on the place of a gcosyncline is the rising 

 of a median anticline. It is in this connection not to be overlooked that with a raising of 

 an anticline, as a rule, the formation of deeper depressions on both sides goes hand in 

 hand ; and if we consider the small thickness of the conglomerate bands (10-12 feet), 

 their obvious local distribution, and the general and great prevalence of the fine grained 

 shales and slates over the grits and conglomerates we cannot avoid the inference that the 

 total lithologic aspect of the rocks remains that of deeper water deposits notwithstanding 

 these intercalations. If Dale asks [p. 297]: " Why should the Ordovician sediments thin out 

 at the west? . . . Were the Ordovician sediments originally thinner on the slate belt, i. e. 

 was it an area of deeper water and, therefore, of less sedimentation, or, as previously sug- 

 gested, was the slate belt a land surface submerged but here and there, with deeper water 



