GEOLOGY OF SARATOGA SPRINGS AND VICINITY I4I 



We have represented in figure 15 the events going on in the 

 two troughs, as far as the Saratoga and Schuylerville quad- 

 rangles are concerned, during Cambric and Ordovicic time, where 

 the shaded periods represent emergences and the unshaded the 

 submergences. It is seen at once that frequent oscillations took 

 place in both basins and that the invasions of the sea and with- 

 drawals did not take place simultaneously in both basins, but at 

 very different times and apparently independently of each other. 

 It appears, however, that there is recognizable a certain approxi- 

 mate alternation of the invasions of the sea in the two basins, indi- 

 cating an east-west shifting of the seas in the troughs, such as has 

 been observed in more complete development by Ulrich (1911, page 

 543) in the Ordovicic seas of the Appalachian valley troughs in 

 east Tennessee. Moreover, the invasions came partly from the 

 northeast or Atlantic basin and partly from the Gulf and Pacific 

 basins. 



The Lower and Middle Cambric time finds the western trough 

 entirely drained of the sea, while at the same time a great mass 

 of sediments was deposited to the east, the Georgian in the Levis 

 trough, and the Acadian in still more easterly troughs, and possibly 

 also to a limited extent in the Levis trough. This invasion came 

 from the north. 



In the Upper Cambric the scene of submergence shifted entirely 

 into the neighboring westerly trough, where invasions first from 

 the north and then from the southwest brought the Potsdam sand- 

 stone, the Hoyt limestone and Little Falls dolomite, while the 

 eastern trough or Levis basin was at the same time raised above 

 sea level. 



During Beekmantown and Chazy time that part of the western 

 trough now exposed was apparently drained in the area of the 

 two quadrangles here described, the rocks of the two formations 

 being absent between the Little Falls dolomite and the Amsterdam 

 limestone. They are, however, present but a short distance north in 

 the Ticonderoga-Crown Point region, and the sea in both the 

 Beekmantown and Chazy times, nearly reached the quadrangles 

 in this basin from the north, or it actually reached there in 

 the more eastern, deeper parts of the trough which are now 

 buried under the overthrust shales of the eastern troufrh. The 

 sea did reach into this latitude and beyond, coming from the 

 north, in the Levis trough, where the Schaghticoke and Deep Kill 

 graptolite shales and possibly also the Bald Mountain limestone 



