12 NEW YORK STATE MUSEUM 



in the extreme folding it has undergone, seems to be essentially con- 

 formable also to the underlying series. Conformably over this lies 

 the great thickness of the mica schist which occurs abundantly in 

 the region south of Peekskill to New York city. These are the 

 equivalents of the Lowerre quartzite, Inwood limestone and Man- 

 hattan schist of former reports. 



4 In other places, and commonly on the northern border of the 

 Highlands and in the Peekskill creek valley a similar succession lies 

 v/ith striking unconformity on the tilted gneiss or as sometimes 

 happens, is so faulted as to have obliterated the original relationship. 

 The series at such places, above the unconformity from bottom to 

 top is : a fine quartzite, 300' to 600', a fine grained banded limestone, 

 about 1000', overlain by a great but unknown thickness of shales, 

 slates, phyllites and shaly sandstones. These series at the localities 

 where their relationships are known are equivalents of the Cambric 

 qnartzites, Wappinger limestone and " Hudson River slates " of 

 other reports relating to the district north of the Highlands. 



5 It seems reasonable that these two types of occurrences rep- 

 resent two wholly different sedimentary groups, one much the 

 older and together with the older gneiss, forming a Precambric 

 group; the other forming a Cambric to Lower Siluric group; the 

 two separated from each other by a time interval of unknown value. 

 The region has been diligently searched for a satisfactory contact 

 of the upper members of the two series with each other but thus far 

 without success. All members of the older series are injected with 

 igneous masses, on the contrary the upper series is nowhere cut by 

 any kind of eruptive except by the Cortlandt series which is the 

 latest type in the entire region. 



6 There is a series of faults of great displacement bordering the 

 Highland belt both on the north and south, in the vicinities of 

 Cornwall on the north and Peekskill on the south. This has allowed 

 movements of considerable areas as blocks and accounts for much 

 of the abruptness of the change along the southern margin especially 

 from later sediments to older gneiss. This faulting is later than 

 Lower Siluric and was accompanied by the Cortlandt igneous ac- 

 tivity. No later geological deposits occur in the district except the 

 drift. 



7 All the larger stream valleys were in preglacial time eroded 

 below the sea level. Some are filled with 200' to 300' of glacial 

 drift. It is more than 375' to bed rock in the Hudson river oppo- 

 site Storm King. 



