[Annals N. Y. Acad. Sci., Vol. XXI, pp. 11-86, PH. III-VI. 15 May, 1911] 



GEOLOGY OF THE COKTLANDT SEKIES AND ITS EMEEY 



DEPOSITS 1 



By G. Sherburne Kogers 



(Presented in abstract before the Academy, 6 March, 1911) 



CONTENTS 



Page 



Introduction 11 



Historical review 13 



Correlation : 19 



Petrology 20 



Plutonic rocks 20 



Dike rocks 47 



Abnormal contact rocks 50 



Inclusions 52 



Structural geology 54 



Relations of the types, with analyses 57 



Geology of the emery 66 



Petrography of the emery and associated rocks 68 



Types of occurrence 72 



Origin 77 



Summary 85 



Introduction 



The Cortlandt Series is a small but remarkably complete igneous 

 complex, lying to the south and east of Peekskill, N. Y., or about 35 

 miles north of New York City. It was so named by James D. Dana, the 

 first geologist to bestow upon it any particular attention, because of the 

 approximate coincidence of its boundaries with those of the township of 

 Cortlandt, the most northwesterly in Westchester County. More careful 

 work upon its extent emphasizes the roughness of its conformation with 



1 The writer desires to acknowledge his obligation to Prof. J. F. Kemp, who suggested 

 the subject of this investigation and under whose general direction it was carried out. 

 To Prof. C. P. Berkey, the thanks of the writer are due for valuable advice and many 

 suggestions generously imparted in the course of the work ; and to Dr. M. A. Lamme for 

 assistance and advice in connection with some of the chemical problems encountered. 



(11) 



