40 NEW YORK STATE MUSEUM 



It is possible that similar faults to those mentioned occur on the 

 area north of the plateau escarpment, but their existence is not 

 known. The covering of mantle rock is so continuous and the 

 exposures of the rock so limited in number and size that no fault 

 planes have been observed ; they may or may not be present. 1 



IGNEOUS ROCKS 



At several places in the city and in the vicinity molten rock was 

 forced up from the deeper portions of the earth through cracks or 

 fissures to or near the surface, forming dikes of igneous rocks. One 

 of these dikes in the city is exposed on Green street near Lodi and 

 has been traced by means of excavations for a mile or more from 

 that point through the city. If it were not for the heavy covering 

 of mantle rock concealing it, it could probably be traced much 

 farther. The excavation for the Dewitt reservoir a few miles east 

 of the city is in a dike of igneous rock similar to that on Green 

 street. These peridotite dikes and others of similar character are 

 described in the following pages in a paper by B. W. Clark on the 

 Peridotite Dikes of Central Nezv York. 



PHYSIOGRAPHIC FEATURES 



The physiographic features of the Syracuse region, while quite 

 varied in character, are all comprised in two of the great physio- 

 graphic regions of the State, namely, the Alleghany plateau on the 

 south and the Ontario lake plains on the north. There is sufficient 

 complexity of detail in each of these regions to give variety and 

 interest to the scenic features, some of which are quite striking. 

 The greater part of the Syracuse area is on the lake plains ; only a 

 small fraction along the southern margin catches the northern edge 

 of the plateau. 



Since the northern edge of the plateau has been beveled by the 

 ice and other weathering agencies, the part on the Syracuse quad- 

 rangle does not nearly reach the maximum height of the plateau. 

 The highest point on the quadrangle is a little over a thousand feet 

 above sea level, while farther south the plateau rises to about three 



1 For further account of these faults and folds, see Luther, Economic 

 Geology of Onondaga County. 15th Ann. Rep't N. Y. State Geologist, 1895. 

 Also P. F. Schneider, Note on some overthrust faults in central New York. 

 Am. Jour. Sci., v. 20, Oct. 1905, and The Marcellus Fault, Onondaga 

 Academy of Sciences, 1899. 



