142 NEW YORK STATE MUSEUM 



of upper Beekmantown age were deposited in Beekmantown time; 

 and after a brief emergence, the Normanskill shale of Chazy age, 

 which in its turn was followed after another short emergence by 

 the sea depositing the Upper Normanskill shale with the Rysedorph 

 Hill conglomerate and the Snake Hill shale. It appears that this 

 whole group of Ordovicic seas of the Levis trough invaded from 

 the north. The north connection is shown by the faunas and areal 

 distribution of the Schaghticoke, Deep Kill and Normanskill shales, 

 by the Atlantic faunas of the Rysedorph Hill conglomerate, and it 

 is suggested by the fauna of the Snake Hill shale. Some of these, 

 as the Deep Kill and Normanskill seas, had also connection with 

 the Pacific ocean. 



LATER PALEOZOIC HISTORY 



Withdrawal of marine waters from the Saratoga region followed 

 the deposit of the Indian Ladder shales and for the latter part of 

 the Ordovicic period the region was above water. Then followed 

 a time of considerable disturbance and uplift, the so-called Taconic 

 revolution. Along a belt of country east of Saratoga the Ordovicic 

 rocks were folded and upturned. About Saratoga this disturbance 

 had no effect beyond giving the region somewhat increased alti- 

 tude. During the following Paleozoic periods, Siluric, Devonic 

 etc., the region continued its oscillations of level, but the times of 

 depression did not carry the bottoms of the troughs below sea 

 level. Paleozoic rocks younger than the Ordovicic, and all Meso- 

 zoic rocks, are absent from the western trough. It remained a 

 trough during all this great lapse of time, but it remained above 

 the level of the sea, even when its altitude was the lowest. Siluric 

 and Devonic seas came into southern New York, but probably the 

 waters of none of them covered Saratoga. 



Apparently, however, the district remained at low altitude dur- 

 ing all this time. No great thickness of Ordovicic rocks has been 

 eroded from its surface. These shales of the upper Ordovicic are 

 weak rocks and would be readily worn away under conditions of 

 high altitude and free drainage. That they remain in such thick- 

 ness as they have over so much of the district is demonstrative of 

 small erosion since they were 'laid down. 



It is quite probable that during oscillations which depressed the 

 western trough, continental deposits accumulated in it and were 

 subsequently worn away during the intervening periods of greater 

 altitude. It is also possible that the overthrust shales of the more 



