Report of the State Geologist. 155 



several geological formations constituting the mass accurately 

 laid down upon the map. This work has been accomplished 

 and a careful study of the escarpment made by myself and 

 assistant, Mr. N. H. Darton, first, from Howe's Cave, by 

 way of Schoharie, Berne, Knox, the Indian Ladder, etc., to 

 Clarksville. Along this line of observation the rocks of the 

 Lower Helderberg, together with the representatives of the 

 Niagara and Clinton groups, with the waterlime at their base, 

 rest in apparent conformity upon the rocks of the Hudson River 

 group below, which are themselves undisturbed along the eastern 

 and western line to the outcrops and dip gently to the southward 

 between the limits above indicated. The first indication of a 

 disturbance occurs to the north, and northwest of Clarksville, 

 where, following the main line of the escarpment, the rocks of 

 Helderberg dip beneath the surface of the valley, while the base 

 of the formation diverges to the northwestward, ending in a 

 broad promontory known as Stony Hill, leaving a deep indenture 

 suggestive of a partial faulting of the strata along this line of 

 deep erosion. This outlying area has often been taken for a cir- 

 cumscribed outlier of these formations, and on cursory examina- 

 tion presents that aspect. Following the line of outcrop south- 

 easterly from its exposure on Stony Hill the escarpment, which 

 is there obscured by a great accumulation of drift material upon 

 its northern face, gradually becomes conspicuous, and before 

 reaching South Bethlehem, and at that place, also farther to 

 the southeast, this escarpment reaches its greatest elevation and 

 acquires its boldest features. It is in the neighborhood of South 

 Bethlehem also that we first find evidence of the unconformity of 

 the Helderberg rocks and the Hudson River shales where the latter 

 present evidence of having been uplifted, folded or contorted before 

 the superincumbent limestones were deposited. One interesting 

 example in the bank of a small creek presents an exposure of the 

 shales and limestone which shows that the lower beds of the 

 latter, corresponding to the Tentaculite lavers of the Lower 

 Helderberg, are infolded with the slate, apparently due to an over- 

 thrust fault; the entire exposure presenting the strongest evi- 

 dence of unconformity. . 



