of the Northern Catskill Mountains. 153 



The two sections agree in three particulars — the compact, 

 blue, pebbly till below ; the zone of stratified materials near the 

 center ; and the less compact, yellowish blue, bowldery till 

 above. 



The upper member of this series is puzzling. It differs 

 greatly both in color and in texture from the blue till and the 

 clay below. Is it possibly the product of a later glacial epoch ? 

 Or does it represent the results of ice moving from the south 

 overriding the previously deposited blue till ? These are ques- 

 tions which must be left unanswered. Of possible significance 

 in this connection is the fact that the surface of the deep valley- 

 filling from Manorkill Falls at least four miles northward is 

 remarkably smooth and nearly level, and stands at an elevation 

 of about 1300 feet (fig. 4). It has occurred to me that this flat 

 may be either a surface smoothed by overriding ice or a wave- 

 determined level in an old lake bottom. The surface of the 

 flat is covered locally by lake clay to a depth of several feet. 



An extremely significant section was revealed in 1909 in 

 the stream bed just below the lowest houses along Fly Brook 

 about one mile northwest of Prattsville. Excavations for a 

 railroad abutment were in progress. At the road a pit about 

 six feet deep showed coarse bowldery red till made up entirely 

 of local materials — in this respect resembling the till which 

 covers the surface all the w r ay up the valley of Fly Brook, and 

 also that in the Devasego morainic loop. Another pit in the 

 bottom of the valley on the west side of the stream showed 

 some six feet of local red stream gravel and red bowldery till 

 underlain by a pebbly blue clay containing a few pebbles, 

 mostly scratched limestones and other rocks foreign to the 

 region. This blue clay is unquestionably the same as the drift 

 which makes up the bulk of the moraine near G-ilboa, and con- 

 trasts strikingly with the overlying local red till. 



This section makes it certain that ice from the north has at 

 one time pushed at least as far south as this, depositing the 

 blue clay, and that subsequently ice moving from the south 

 down Schoharie Creek or down Fly Brook (or both) has 

 deposited the red bowldery till. Whether this indicates two 

 distinct glacial epochs or merely fluctuations of ice front dur- 

 ing a single epoch is another unsettled question. 



Above the Prattsville loop, in the valley of Batavia Kill, 

 there is a remarkable series of moraines, all of them apparently 

 convex dovm valley (toward the west). At Red Falls, Ash- 

 land, East Ashland, Windham, and half way between Union 

 Society and East Windham, the moraines are especially strong. 

 They appear to have been developed in connection with ice 

 that moved from the Hudson Yalley lobe across the Oatskill 

 Escarpment, mainly through the gap at East Windham and 



Am. Jour. Sci.— Fourth Series, Vol. XXXIX, No. 230.— February, 1915. 

 11 



