GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 



II 



gations greatly extended our knowledge regarding the age of the 

 Wappinger limestones, particularly those of the Wappinger creek 

 belt. 



In 1886 J. C. Smock, as a part of a preliminary report on the Pre- 

 cambric rocks of the Highlands east of the Hudson, discussed the 

 gneisses of the Fishkill mountains. But notwithstanding these con- 

 tributions, the areal geology has not been mapped in detail up to 

 the present time. 



STRATIGRAPHICAL TABLE 





SEDIMENTARY 



ERUPTIVES 





Formations 



Terranes 





Alluvium 



Recent 





Quaternary 



Terraces 

 Kames 

 Drumlins 

 (Unconformity) 



Glacial 







" Hudson River " slates, 

 grits and phyllites 



Utica? 

 Trenton 





Ordovicic 



Wappinger limestones and 

 dolomites, in part 



Trenton 



(Disconformity) 



Beekmantown 



Hortontown hornblende 

 rock 



Cambric 



Wappinger limestones and 

 dolomites, in part 



(Disconformity?) 

 Potsdam 



? 



Georgian 





Poughquag quartzite 

 (Unconformity) 



Georgian 





Precambric 



Gneisses of the Fishkill 

 mountains and inliers of 

 these rocks 



" Grenville " 



Shenandoah granite 

 Bald Hill granite gneiss 



THE PRECAMBRIC GNEISSES 



DISTRIBUTION 



Within the Fishkill mountains the boundary of these rocks, as 

 shown by the map, follows closely the lower contour lines of the 

 spurs. 



The Glenham belt is an inlier of these rocks. It has the same 

 trend as the ridges of the gneisses in the Highlands and extends as 

 a narrow strip from a point just north of the carpet mill at Glenham 

 northeastward to '' Vly mountain."^ 



1 The hill marked Fly mountain on the map is just southeast of what, 

 in this vicinity, is called Vly mountain, corrupted to Fly mountain. The 

 swamp just south of the eminence doubtless suggested the name (Vly- 

 swamp). 



