a-'; 



Education Department Bulletin 



Published fortnightly by the University of the State of Nevr York 



Entered as second-class matter June 24, 1908, at the Post Office at Albany, N. Y., 

 under the act of July 16, 1894 



No. 492 



ALBANY, N. Y. 



April i, 1911 



New York State Museum 



John M. Clarke, Director 

 Museum Bulletin 148 



GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 



C. E. GORDON 



PAGE 



Introduction 5 



Location and other general features 



of the quadrangle 6 



Topography .- 7 



Drainage 8 



General geology. . 9 



Previous geologic work. 10 



Stratigraphical table 11 



The Precambric gneisses 11 



The Hortontown basic eruptive 

 and associated metamorphic 



rocks S7 



The basal quartzite (Poughquag) 39 

 The Wappinger (Barnegate) lime- 

 stone 48 



■I 



UnU OF 



(|Pethnolocy. 



irtfknrv 



PAGE 



The Wappinger creek belt 48 



The Fislilcill limestone 70 



The " Hudson River " slate group 82 



Preglacial history of the drainage 96 



Glacial geology . 99 



Retreat of the ice sheet 100 



Postglacial erosion 104 



The present depression 105 



Other drainage features and adjust- 

 ments 105 



Land forms 105 



Economic geology 106 



Bibliography no 



Index 117 



%\(\^A'^ 



ALBANY 



UNIVERSITY OF THE STATE OP NEW YORK 

 I9II 



M248r-Nio-i5oo 



