GEOLOGY OF SARATOGA SPRINGS AND VICINITY I43 



easterly troughs may have formerly extended farther west than 

 they do now, and have covered the present exposures of the rocks 

 of the western trough, from which they were afterward worn 

 away. But this does not alter the fact that the Ordovicic shales 

 are the last marine deposits known to have been deposited in the 

 region ; that the time which has elapsed since the close of the 

 Ordovicic is enormously long; and that it seems inconceivable that 

 these shales could remain over so much of the district and in such 

 thickness, if the trough had ever had a high altitude for any con- 

 siderable length of time. 



CLOSING STAGE OF THE PALEOZOIC 



It has long been held by geologists that the closing stages of the 

 Paleozoic were, in eastern North America, a time of great earth 

 disturbance. The district was uplifted and titled and at the same 

 time the rocks were greatly folded and faulted by compressive 

 forces. Folded rocks characterize the Appalachian district from 

 Alabama to New York, and thence northeast to Gaspe. 



It is quite certain that widespread uplift and Appalachian folding 

 occurred at this time; but it would seem also that the preliminary 

 stages of the folding, at least, had taken place long before. The 

 sagging troughs of which we have been speaking, separated from 

 one another by tracts of relative uplift, were the initial stages of 

 this folding, which had been in progress all through the Paleozoic, 

 as recently urged by Ulrich.^ 



The Paleozoic deposits of the lower Mohawk trough, the Western 

 basin deposits of this report, were for some reason not greatly 

 folded. They lie nearly flat today. They lay either too far west 

 or without the zone of folding; or else the unyielding mass of the 

 Adirondacks, which lay back of them, acted to prevent folding. 



Did the thrust faulting which has carried the rocks of the East- 

 ern basin into our district take place at this time, or not till later? 

 We can not positively answer this question as yet; but we are in 

 agreement with Ulrich in thinking that much of it is of later date 

 and possibly very much later. 



MESOZOIC HISTORY 



During the entire Mesozoic the Saratoga regi©n remained a land 

 area. During the earlier portion of the time certain troughs along 

 the east margin of the Ap])alachian region su])sided and received a 



^Geol. Soc. Am. Ihil., 22:436-42. 



