FIFTH REPORT OF THE DIRECTOR 1908 



15 



ones during the later period of mountain making. In the town 

 of Fishkill, lying within the younger rocks and extending from near 

 the base of the Bald Hill spur northeastward for a distance of 5 

 miles and terminating in a faulted block known as " Fly mountain," 

 is a narrow inlier of Precambric rocks which will be shown to be a 

 part of the Highlands. 



Reconnaissance through the Highlands indicates the essential 

 similarity between the basal gneisses of this quadrangle and the 

 rest of the northern Highlands. Within the quadrangle there is 

 no evidence of more than one sedimentary series. Considerable 

 shearing has occurred and is considered responsible for some of 

 the foliation. Later faulting and shearing have obscured earlier 

 features. There is given as a result of pressure always applied in 

 the same general direction and from the factors just mentioned an 

 isoclinal character to these rocks that simulates an immense mono- 

 clinal series of sediments. Continuity has been broken, and repe- 

 titions by earlier folding have been sheared out, by faulting. If 

 the identification of the stratum of serpentinous rock, interbedded 

 with the gneiss, as an altered limestone be correct, the general 

 resemblance which these gneisses have to the other basal gneisses 

 of the Highlands has confirmation in that fact. Recent work by 

 Eerkey 1 in Manhattan shows limestones interbedded with the Ford- 

 ham gneiss, which strengthen the correlation previously made by 

 him of the Fordham gneiss with the gneisses of the Highlands. 



Poughquag quartzite. This formation which intermittently 

 appears, overlying the gneisses along their northern border, from 

 the type locality at Poughquag, Dutchess co., to the Hudson river 

 is undoubtedly of Lower Cambric age. Fossils have not been 

 found in this formation, but the blue limestone immediately over- 

 lying it, into which it grades, has yielded the opercula of 

 Hyolithellus mi cans. The relationship of the quartzite to 

 the gneiss and of the quartzite to the overlying limestones and 

 calcareous shales as seen south of Johnsville, in the East Hook, 

 are very similar to those near Stissing mountain, at Stissing Junc- 

 tion and Attlebury, farther north in Dutchess county, which have 

 been proved to be Lower Cambric by the discovery of Olenellus in 

 the quartzite and of opercula of H . (nicans in the overlying 

 limestone. The rusty friable Olenellus quartzite described by Wal- 

 cott and Dwight and found by the writer west of Stissing Junction 

 could not be located in the Fishkill mountains. 



1 Science N. S. v. 28, no. 730, p. 936. 



