THE GEOLOGY OF THE SYRACUSE QUADRANGLE 23 



others. Except where buried under the floor of Onondaga valley 

 and Butternut valley, it forms a continuous outcrop across the quad- 

 rangle. In most places it is the top layer at the northern edge of 

 the plateau escarpment, as in the steep cliffs around the Green lake 

 and Blue lake basins and along many of the deep depressions cut 

 into the plateau. In many places the upper surface of this rock free 

 from any soil covering extends over a width varying from a few 

 feet to several hundreds of feet back from the cliff edge. The 

 older residual material was scraped off by the glacier and the sur- 

 face washed clean by the glacial waters. There has been very little 

 disintegration from the temperature changes. Decay goes on almost 

 entirely by solution and the rock is such a pure carbonate of lime 

 that any slight residual matter left on the surface is washed away 

 by the rains. As in other limestone regions, disintegration has been 

 by the descending ground waters acting along the joint planes which 

 have been opened up in this way into fissures varying from a few 

 inches to several feet in width and extending down in places more 

 than a hundred feet below the surface. These fissures in some places 

 open up into caverns of some size. At the " Syracuse caves," 3 

 miles southeast of the city, some of these fissure caverns have been 

 explored to a depth of more than a hundred feet and some hun- 

 dreds of feet in length. Where this fissuring has been intensified 

 it produces the well-known karsten topography. 



In a few places there has been a little deposition of calcite on the 

 walls of the fissures, but in general the deposition is very slight in 

 comparison with the solution since most of the material dissolved 

 has been carried away into the streams or deposited in the deeper 

 portions of the underlying rocks. 



Some of these fissures are open enough at the top to permit large 

 quantities of snow to enter them during the winter months, and 

 remain in the form of snow and ice during the greater part of the 

 summer, forming what is known locally as the " ice caves." These 

 occur in the cliffs around Blue lake and at the Split Rock quarries. 



Overlying the lower crystalline portion of the Onondaga limestone 

 is a thickness of 60 to 70 feet of a compact blue limestone contain- 

 ing many scattered concretionary masses of chert and hornstone. 

 In the older reports this is known as the Corniferous because of the 

 prevalence of the hornstone. The chert is very irregularly scat- 

 tered through the limestone, yet it occurs in sufficient quantities and 

 so distributed that no considerable body of the stone is anywhere 

 entirely free from the chert, and thus it seriously injures the rock 



