GEOLOGY OF THE NORTHERN ADIRONDACK REGION 



379 



no good continuous section. Northwestward also, about Newport 

 and Poland, the sections stop in the lower Trenton, while away 

 from the creek valley the drift cover is excessive. There is how- 

 ever a very good section in Rathbone brook, near Poland. White 

 measured the section here and states its thickness to be 138 feet, 

 with the Black River in place below. 1 He was unable to deter- 

 mine how great a thickness at the base should be regarded as being 

 below anything shown at Trenton falls, where the base of the 

 formation is not shown. The section also terminates in the 

 Trenton and hence gives only a minimum value to the thickness. 

 The incompleteness of the section hereabout is exceedingly unfor- 

 tunate, since in the gorge of West Canada creek at Trenton falls, 

 the type locality of the formation and distant only 14 miles from 

 Middleville, the section shows a thickness of 275 feet (Prosser), 

 or 284 feet (White), with neither base nor summit exposed. 2 

 Reference may be made to their papers for the details of the sec- 

 tion, which consists mainly of thin bedded, dark blue limestones, 

 with considerable admixture of the gray, crystalline beds, and 

 with occasional massive layers; the whole capped by the 26 feet 

 of massive, gray layers at Prospect [pi. 8 and 9]. Underneath 

 this cap considerable shale is intercalated with the thin limestones 

 through a thickness of 60 feet, giving a lithologic combination 

 quite like that of the passage beds elsewhere. Nothing can be 

 learned concerning these in the vicinity, unfortunately. Accord- 

 ing to White the lower portion of the Rathbone brook section 

 underlies the base of the section at Trenton falls, but he does not 

 hazard a suggestion as to the actual thickness involved. It seems 

 however quite safe to say that the Trenton at Trenton falls is 

 approximately 300 feet thick, more than double its thickness at 

 Middleville. 14 miles away to the south of east. Only 27 miles 

 farther to the southeast lies Canajoharie, with its 17 foot thick- 

 ness for the limestone, the minimum for the State. Some of the 

 latter diminution is due to overlapping unconformity, the base 

 disappearing, but in either case it is obvious that the increase 

 west from Middleville is more rapid than is the decrease eastward. 

 Also that the increase in thickness is upward, implying that the 



l N. Y. Acad. Sci. Trans. 15 :S4. 



*15tb An. Rep't State Geol. p.626 and footnote. 



