REPORT OF THE DIRECTOR I912 IQ 



West Branch and Northville ; and in the valley of the West 

 Branch in the vicinity of Whitehouse. 



During the year we have issued a bulletin on the Mineral 

 Springs of Saratoga, prepared by James F. Kemp, in con- 

 nection Avith the series of investigations of the Saratoga district 

 which have been in progress for several years. The region here 

 concerned is covered by the Saratoga and Schuylerville quad- 

 rangles and the rock geology, especially intricate in the latter 

 quadrangle, has now been finally mapped by Doctors Gushing 

 and Ruedemann. Features of special importance in the Schuy- 

 lerville region are the great overthrusts and overturned folds in 

 the Bald mountain district and the problem presented by the 

 Schuylerville volcanic' plug penetrating the Paleozoic slates. The 

 latter has been much debated. The shales about the volcanic 

 mass have been distinctly overthrust and it seems very evident 

 that the eruptive has been involved in this movement. There 

 are reasons for regarding the plug as of Postpaleozoic age and 

 as thrust by lateral shove many miles westward of its original 

 position. 



The investigation of the structure of the shale belt of the 

 Schuylerville and Saratoga sheets has led to the inference that 

 the mineral waters of Saratoga fill a wdde basin below the shale 

 form.ed by the Potsdam sandstone and overlying Cambric and 

 Ordovicic limestones and that the water of the Saratoga springs 

 is derived by filtration through mountain folds about the Hud- 

 son river and carried westward under the thick cover of the 

 Canajoharie shales to the Saratoga-Mount McGregor fault and its 

 branches, where it finds the thinnest cover- of shale and thus 

 escapes. The Ganajoharie shale rapidly thickens southward on 

 account of its dip, and the projecting fault blocks of Precambric 

 rocks close the basin to the northward. 



Outside of this immediate region, the w^ork in the shale belt 

 has further brought out the fact that the thick formation of the 

 Normanskill shale comprises two divisions, a lower one corre- 

 sponding to the Ghazy, and an upper, corresponding to the Low- 

 ville-Black river interval. Normanskill shale graptolites were 

 found in shale intercalated in the grit beds extending many miles 

 along the Hudson about Hyde Park, N. Y., indicating that the 

 shale belt there may be largely of Normanskill age. The broad 

 belt of rocks extending from Schodack Landing to Stockport 

 has hitherto been entered as Georgian on the State map, but 

 the larger middle part of this is now known to consist of Deepkill 



