FETTKE, MANHATTAN SCHIST OF NEW YORK 201 



Merrill's correlation was quite generally accepted as the correct one 

 until 1907, when Dr. Charles P. Berkey^^ published a paper on the basal 

 gneisses of the Highlands, based upon field work done by him in the 

 Tarry town and West Point quadrangles. He does not accept tlie correla- 

 tion of Merrill and others and presents very strong evidence tfiat the 

 Inwood-Manhattan series south of the Highlands and the Poughquag- 

 Wappinger-Hudson Kiver series, to the north, are not equivalent. Ac- 

 cording to his position there are then the following six formations in 

 relative order from the top downward overlying the basal gneisses : 



(6) Hudson River phyllite or slate, which is very thick, 



(5) Wappinger fine-grained blue and white banded limestone, about one thou- 

 sand feet thick, 



(4) Poughquag fine-grained quartzite, three hundred to six hundred feet thick. 



(3) Manhattan coarsely ciystalline mica schist, which is very thick. 



(2) Inwood coarsely crystalline limestone, two hundred to eight hundred feet 

 thick. 



(1) Lowerre thin schistose quartzite, zero to one hundred feet thick. 



The Lowerre quartzite south of the Highlands is closely related to the 

 underlying gneiss, whenever it appears, which is not very frequently. It 

 is thin when it does occur, rarely exceeding one hundred feet in thickness, 

 and is always conformable with the associated gneiss. The Poughquag 

 quartzite north of the Highlands on the other hand is usually much 

 thicker, three hundred to six hundred feet, and rests with a marked uncon- 

 formity upon the underlying gneiss. The relationship of these forma- 

 tions in the region northeast of Peekskill in the Peekskill Creek and 

 Sprout Brook Valleys led Dr. Berkey to conclude that the two series could 

 not be regarded as the same in age. The quartzite-limestone-phyllite 

 series of the Peekskill Valley section he considers to belong to the Pough- 

 quag- Wappinger-Hudson Eiver group, representing a down-faulted block 

 of these once overlying formations into the older strata. A mile to the 

 northwest across a ridge another belt of limestone occurs in the Sprout 

 Brook Valley. This limestone is coarsely crystalline in contrast with the 

 finely crystalline limestone of the Peekskill Creek section and contains 

 silicate minerals and pegmatite intrusions which are absent in the latter. 

 No quartzite whatever occurs in either margin of it, while the Peekskill 

 Creek limestone has five hundred feet of quartzite conformably beneath it. 

 The limestones of these two valleys can hardly be considered the same, 

 and, if the Sprout Brook limestone is the equivalent of the Inwood, as 

 Dr. Berkey thinks, the less metamorphosed Peekskill Creek limestone is 



" "Structure and stratigraphic features of the basal gneisses of the Highlands." N. Y, 

 State Mus. BuU. 107, pp. 361-378. 1907, 



