138 NEW YORK STATE MUSEUM 



8 It seems impossible to avoid the conclusion that the Manhattan- 

 Inwood series has attained its petrographic and structural character 

 under great load. Its metamorphism and deformation are such as 

 to indicate reorganization under very heavy pressure. Something 

 must have rested upon these members to develop the necessary 

 pressure. The most violent deformation which one sees north of 

 the Highlands has not developed such quality in the Hudson River 

 formation. The chief failure in that case is doubtless not the com- 

 position and not lack of deformation influences, but chiefly lack of 

 load or lack of special igneous influences or both. There was not 

 sufificient pressure to cause complete reorganization. Perhaps also 

 there was not sufificient time, but if the Manhattan-Inwood series 

 is the saine age as the Hudson River-Wappinger, the same liinita- 

 tion with respect to time would apply to it. If it is the same series as 

 the Hudson River-Wappinger, then it is difficult to conceive of a suf- 

 ficient load in the stratigraphic column represented to account for 

 the metamorphism observed in the Manhattan. The schists are 

 thoroughly recrystallized rather than sheared or granulated and have 

 a prominent development of garnet and other typical reorganization 

 products, all of which point to the same general conclusion. 



Summary. The items enumerated and discussed on this correla- 

 tion problem may be summarized as follows : 



A Points favorable to the identity of the Hudson River-Wap- 

 pinger-Poughquag and the Manhattan-Inwood-Lowerre series of 

 sediments and metamorphosed sediments : 



1 Similarity of succession and original character. 



2 Occurrence of gneisses immediately below. 



3 Both series much deformed and modified. 



4 Near approach of outcrops of the two series so that one can be 



traced almost into the other. 



5 Reported increase of metamorphism of the Hudson River 



formation toward the east, until near the Connecticut line 

 it is practically identical in character with the Manhattan 

 schist. 



6 Failure of the structural relation that ought to be expected 



where the two series approach each other, especially the 

 failure of either entire and actual unconformity or a simple 

 transition. 

 B Points of dissimilarity which seem to support the hypothesis of 

 different age and entire independence of the two series : 



I The strikingly different physical appearance and petro- 



