GEOLOGz OF SARATOGA SPRINGS AND VICINxrY I39 



The Amsterdam is the only Black River formation deposited 

 over the Saratoga region. The margins of the Lowville and Water- 

 town troughs did not quite reach the district, and the Amsterdam 

 rests on the Little Falls dolomite. It is the oldest Ordovicic for- 

 mation of the quadrangle. Between the deposition of the two 

 the region stood as a land area on the margin of the Champlain 

 trough. The small amount of erosion of the Little Falls sur- 

 face during this long interval is indicative of low altitude of the 

 land. 



The pure limestone of the Amsterdam denotes also low alti- 

 tude of the neighboring land. The abundance of marine fossils 

 shows plentiful life in the waters. 



Uplift followed Amsterdam deposition, the Saratoga region pass- 

 ing slightly above sea level. 



Succeeding this uplift came the Trenton submergence. At first, 

 beds of limestone and of blackish shale alternated with one an- 

 other ; but the limestone soon ceased and the great thickness of 

 the Canajoharie shale of lower Trenton age slowly accumulated 

 in the subsiding trough. The fossils are chiefly graptolites ; open 

 sea forms swept into the trough by marine currents which ran 

 through it. Conditions were not favorable for an abundant and 

 diversified marine fauna. 



During this same time Trenton limestones were being deposited 

 on the west side of the Adirondacks, in clearer seas which swarmed 

 with marine organisms. Conditions on the two sides of the region 

 were thus sharply contrasted. 



In middle Trenton time the deeper Canajoharie sea which ex- 

 tended from the Mohawk valley northward through the Chazy- 

 Saratoga basin into Canada and southward through the Hudson 

 river region and as far south as the southern Appalachians, was 

 probably drained for a brief period in this region, but soon again 

 the shallow sea of the Schenectady period extended through the 

 trough northward to an unknown extent, but undoubtedly across 

 the Saratoga and Schuylerville quadrangles. The bottom of this 

 trough kept sinking gradually, so that upward of 2000 feet of 

 shallow water deposits could be accumulated in it in Schoharie and 

 Schenectady counties. 



In the following Utica period this region was probably again 

 emerged, for no Utica deposits have as yet been recognized in the 

 lower Mohawk and Hudson valleys, the so-called Utica beds of 

 these regions all being now known to be of Canajoharie age. It 



