24 P. F. Schneider — Ei^uj^tive Dikes in Syracuse. 



Art. Y . — New Exposures of Eruptive Dikes in Syracuse^ 

 N. Y. ; by Philip F. Schneidee. 



Igneous rocks in the horizontally stratified Paleozoic beds 

 of Central New York are too rare to pass unrecorded ; and 

 when, recently, excavations in Syracuse for the Butternut street 

 trunk sewer disclosed another of these occurrences in a new 

 locality and at so great a depth that ordinary excavations had 

 not reached it because of the thickness of the overlying drift, 

 it became important that some permanent and available record 

 should be made of the same. 



The eruptive rock was first noticed April 16, 1901, some 

 three days after it was first penetrated. At this point, a short 

 distance beyond the place where the sewer crosses Highland 

 St., the eruptive rock occurred in the bottom of the trench and 

 was dug into only to a depth of some two feet. It was over- 

 laid by nearly three feet of decomposed peridotite, which had 

 been entirely changed to a soft greenish-yellow earth. As the 

 excavation progressed to the east of Highland St., the work- 

 men penetrated deeper into the rock, which for some distance 

 presented a slightly stratified appearance suggesting a sheet 

 branching from the dike proper, which subsequent excavations 

 proved to be the case. 



The dike itself was first encountered 126 feet east of the 

 center of Highland st., and was so hard and firm as to be 

 removed with great difiiculty. The width of the dike is 86 

 feet and it comes up to within ten feet of the natural surface. 

 From its location in the trench, which was five feet in width, 

 the strike of the dike appeared to be N. 5° E. There was 

 scarcely any sheet to the east of the dike, but to the westward 

 it extended over three hundred feet. 



The rock in the main dike, with the exception of the upper 

 two feet, is perfectly hard and firm. It is of a dark green 

 color, some of it being almost black, and contains an abund- 

 ance of apparently jet black crystals. The upper portion, 

 immediately beneath the drift, had changed to a soft greenish- 

 yellow earth, in some places to a yellowish earth. The fact 

 that the lower portion of the drift contained much of the 

 serpentinous earth mixed with it would suggest that a con- 

 siderable area was covered with eruptive matter. The typical 

 rock contained few inclusions as compared with that at De- 

 Witt, N. Y., or even that in the Syracuse dikes at Green st. 

 The softer rock of the sheet, however, contained many of 

 them. No prominent fossils were found in any of these 

 inclusions, whereas in the rock at DeWitt they were very 



