GEOLOGY OF THE NEW YORK CITY AQUEDUCT 



lOI 



Mesozoic 



Erosion to peneplain 



Unconformity 



A long interval including two mountain-making epochs 

 and at least one period of general sedimentation 



Paleozoic 



Hudson River slates 



Proterozoic 



^-Wappinger limestone 

 ^ Poughquag quartzite 



Ordovicic 



Cambric \ 



Unconformity 



A long interval including mountain folding, igneous 

 injection, erosion, and perhaps other sedimentations 



' The metamorphosed schists, limestones, quartzites 

 etc., together with accompanying intruded igneous 

 masses — forming the basal gneisses of the High- 

 lands 



The evidence of such succession and history gathered from the 

 scattered outcrops of rock in the immediate area, is nowhere better 

 shown than in the field covered by this investigation. 



Structure 



When such outcrops as are known are plotted and organized, sev- 

 eral important facts become clear. 



1 The folds run with remarkable persistence northeast and south- 

 west. 



2 The succession in many places is not normal. Often a whole 

 formation or even two of them are missing and formations that 

 should be separated are brought side by side. Faulting therefore is 

 prevalent and the occurrences show that these large fault lines 

 usually run northeast and southwest. 



3 A consideration of the dips of the strata shows that most of the 

 folds are overturned as if pushed by some general movement from 

 the southeast. 



4 This same movement causes the faulting to be largely of the 

 overthrust type, and in some cases the lateral displacement attained 

 in this way may possibly be several thousand feet. 



5 Isolated " islands " of the older rock formation appear out in 

 the later sedimentary area. They all seem to belong to prolonga- 

 tion of the ranges of the Highlands and their abundance undoiibt- 



