52 



NEW YORK STATE MUSEUM 



CLINTONVILLE DIKES 



In the summer of 1909 Dr Burnett Smith discovered two small 

 dikes near Clintonville, about 15 miles southwest of Syracuse. These 

 dikes occur at the surface in rocks intermediate in age between 

 those at Syracuse and the ones at Ithaca. . Doctor Smith describes 

 these dikes (46) as follows: ''The dikes in question are exposed 

 on the south wall of the Clintonville ravine at a point approximately 

 c;o feet above the level of the Marietta road. The more western is 

 a fine-grained porphyritic rock resembling peridotite. What appear 

 to be serpentine grains, produced by the alteration of olivine, pro- 

 trude from the weathered surface and have the appearance of small 

 pebbles. Another conspicuous feature is furnished by large scales 

 of bronzy mica. This dike has a uniform width of from 7 to 8 

 inches and is displayed for about 12 feet on the south bank of the 

 ravine. On the north side it is obscured by talus. Its plane is verti- 



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Fig. 5 Vertical section of Clintonville dikes, March 23, 1910 

 Sh := shale P^ peridotite dike 



cal while its direction is north and south, agreeing in the latter re- 

 spect with the Ithaca dikes. Wherever examined it presents a very 

 uniform texture, is apparently free from fragments of the sedimen- 

 tary rocks through which it passed, and has produced little contact 

 metamorphism. 



" The second dike lies about 2 feet and 4 inches to the east of the 

 first and was not observed until the wall at this point had been 

 cleaned. It has a width of about 8 inches. Like the first dike, it is 

 vertical and north and south in direction. It differs, however, from 

 the first dike in being much weathered in places and in containing 

 many shale fragments, some of which have a long diameter of 3 

 inches or more." 



In a visit to this dike in the summer of 1910 I found in the shale 

 18 inches east of the two dikes another small dike or stringer parallel 

 to the other two and, like them, following joint planes of the shale. 

 It was less than an eighth of an inch in thickness, which would 

 indicate an extreme fluidity of the dike material, as it was exposed 

 for several feet on the wall of the ravine and continued parallel 

 with the other dikes below the outcrop. 



i 



