GEOLOGY OF SARATOGA SPRINGS AND VICINITY 43 



the Tribes Hill limestone, may have been deposited here and later 

 removed by erosion. The remainder of the Beekmantown was 

 probably never deposited about Saratoga or along the ]\Iohawk. 



Description. The Little Falls dolomite is composed chiefly of 

 rather massive beds of gray dolomite. The larger part of the for- 

 mation consists of dark gray, fine grained beds. Many of these 

 contain some calcite, chiefly as a cement binding the dolomite crys- 

 tals together. On weathered surfaces the dolomite is the more 

 resistent of the two, the calcite is dissolved, leaving somewhat pro- 

 jecting dolomite crystals and giving a porous, sandy appearance to 

 the weathered surface. Beds of this type are best exposed along 

 North Broadway as the road climbs the hill south of St Clements. 



In addition there is a considerable thickness of more coarsely 

 crystalline, lighter colored dolomite in the formation. About Sara- 

 toga such beds form the summit of the formation and are exposed 

 in many places, perhaps best in the Maple Avenue quarry. They 

 are, in general, quite pure dolomite, lacking the calcite cement which 

 occurs so generally in the darker beds (plate 8). 



It is impossible to get any very correct idea of the thickness of 

 the Little Falls dolomite, from the exposures of the quadrangle. 

 There is not sufficient variation in the character of the rock to en- 

 able one to assign the beds of the scattered exposures to their proper 

 horizon in the formation; and faults so abound that nothing like a 

 continuous section of the entire formation exists in the region. At 

 Saratoga Springs the exposures are in a triangular fault block, and 

 the exposed thickness is 119 feet.^ This is the upper portion of the 

 formation and gives no clue to the amount beneath which is lacking. 

 Two deep wells have been drilled at Saratoga with the diamond 

 drill, with careful preservation of the drill cores, one at the Con- 

 gress and the other at the Hathorn spring. We have had the oppor- 

 tunity to study the former, though we have unfortunately not been 

 able to see the latter. Each well went down near the Saratoga fault, 

 and each must rest under the suspicion of having crossed a small 

 branch of the fault in such way as to duplicate part of the well 

 section and increase the apparent thickness. In the Congress well 

 18 feet, 2 inches of drift was passed through, then 18 feet, 7 inches 

 of Amsterdam limestone, after which the entire core of the well, 

 some 281 feet, consisted of Little Falls dolomite. The upper 40 

 feet of this was of the characteristic coarsely crystalline, light 

 colored dolomite which forms the upper part of the formation about 



1 N. Y. State Mus. Bui. 140, p. 108-9. 



