246 ANNALS NEW YORK ACADEMY OF SCIENCES 



!- A chemical analysis made by the writer of the above described speci- 

 mens gave the following composition : 



Analysis of Phyllite 



Per cent 



SiOj 61.04 



Al.Os 15.87 



Fe^Os 1 . 74 



FeO 4.32 



MgO 3.26 



CaO 2.39 



Na^O 1.83 



K,0 3.26 



H2O+ 1.82 



H2O— 09 



CO2 4.24 



TiO^ 91 



Total 100.77 



A lighter colored coarser-grained type was also examined under the 

 microscope. It consists largely of quartz and sericite, with minor amounts 

 of black iron oxides. A little calcite in isolated crystals is also present. 

 Recrystallization has proceeded much further than in the previous case. 

 The sericite flakes are all oriented parallel to the foliation, while the 

 quartz grains are all more or less elongated parallel to it (PL XIV, 

 Fig. 1). An occasional quartz grain reaches a diameter of .5 millimeter, 

 but most of them are much smaller. 



All who have studied this section have correlated these formations with 

 the Poughquag-Wappinger-Hudson River series north of the Highlands. 

 Dr. Charles P. Berkey,^^ who has made the most recent and detailed study 

 of this area, has come to the conclusion that these are not, however, the 

 equivalent of the Inwood-Manhattan series south of the Highlands, as 

 others have thought, basing his view upon the relation of the Peekskill 

 Valley formation to a belt of limestone occupying Sprout Brook Valley to 

 the northwest, which he thinks is the equivalent of the Inwood limestone. 

 A further discussion of these two views will be taken up after the forma- 

 tions north of the Highlands have been described. 



Poughquag-Wappinger-Hudson River Series 



Just north of the Highlands of the Hudson and east of the Hudson 

 Riyer itself, a quartzite to which the name Poughquag has been given 



™ "Structural and Stratigraphic Features of the Basal Gneisses of the Highlands." 

 N. Y. State Mus. Bull. 107, pp. 361-378. 1907. 



