INDEX TO GEOLOGY OF THE WEST POINT OUADRANGLE 



151 



Magmatic absorption or syntexis, 38 



Magmatic differentiation, 33, 35 



Magmatic movement, ^i^ 



Magnetite schist, 58 



Mahopac, 7 



Mahopac granite, 109; description, 



54 

 Manhattan schist, 20, 21, 22, 23, 32, 



43, 124 ; analysis, 61 ; description, 



60 

 Manhattan series, 31, 32, 33, 47, 129 

 Map of the State, pubHshed in iSg6, 



18 

 Mappable formations with their 



petrography, 48 

 Mapping, method of, 27 

 Marble, building stone, 84 

 Mather, W. W., cited, 16 

 Matteawan, 7 

 Mesozoic faulting, 115 

 Mesozoic overlap, later, 117 

 Metamorphic rocks, 5 

 Metamorphics of doubtful age, 60 

 Metamorphics of obscure relation, 



123 

 Metamorphism, 31 

 Mica, 27 



Mineral resources, 82 

 Mohegan granite, 35, 64; analysis, 66 

 Mohegan quarries, 83 



New Jersey correlation, summary, 

 127 



New Jersey folios,* 18 

 New York City area, comparison 

 with, 128 



Olivine-pyroxenite, 68 

 Organic rocks, metamorphosed, 47 

 Oscawana, 58 

 Oscillation, minor, 144 



Peekskill, 7, 9, 58 

 Peekskill creek, 12 

 Peekskill granite, 22, 35; analysis, 



65 ; description, 64 

 Peekskill Hollow, 18, 63, 85, 86 

 Peekskill Hollow creek, 10, 12 



Peekskill-Mohegan granite, 82 

 Peekskill valley section, Catskill 



aqueduct, 104 

 Pegmatite, 19, 2^ 

 Peridotite, 57 

 Petrographic geology, 29 

 Philadelphia area, comparison with, 



128 

 Phyllites, 46, 64 

 Physical geography, 9 

 Physiography, 141 

 Pochuck diorite, description, 51 

 Pochuck gneiss, 19; description, 57 

 Popping rock of Storm King, 97 

 Postglacial changes, 146 

 Post-Grenville volcanism, 108 

 Post-Ordovician erosion, 113 

 Post-Ordovician revolution or de-1 



formation, 113 

 Post-Palaeozoic time, 114 

 Poughkeepsie quadrangle, 21 

 Poughquag quartzite, 22, 46, 86, 112; 



description, 62 

 Poughquag series, 23, 31, 33, 129 

 Precambrian erosion, iii 

 Precambrian rocks, 10, 119 

 Precambrian unconformity, 73 

 Pyrite, 87 



Quartz, 27 



Quartzite, 23, 46, 86 

 Quartzitic gneiss, 58 



Railroads, 7 



Ramapo mountain escarpment, 23 



Raritan folio, 18 



Reservoir granite, 109; description, 



53 

 Revolutionary history, 14 

 Ridgway, Robert, cited, 21 

 Road metal, 88 

 Roads, 9 



Rock formations, 29 

 Rocks, chief types, 2(i 

 Rogers, G. S., cited, 21, 66, 90 



Sand, 88 



Schists, 22, 23, 27 



