NIAGARA FALLS AND VICINITY III 



indicate a nearness to the reef of growing organisms which suppHed 

 the material for these beds. Geodes lined with dolomite crystals 

 occur in this rock, though not so plentifully as at the quarry in the 

 gorge. Below the crystalline limestone is found the cement rock, 

 which is from 4 to 10 feet thick and is quarried in a tunnel under 

 the limestone quarry. 



Owing to the resistant character, the limestone is everywhere ex- 

 posed in the gorge, forming cliffs which are almost invariably per- 

 pendicular. Large blocks of this rock cover the talus everywhere, 

 one of the largest of these being " Giant rock " along the gorge 

 road. This is a block of the upper geodiferous limestone which has 

 fallen from above, and now^ lies with its stratification planes at an 

 angle of about 45°. 



The limestones are well exposed along the gorge road, south of 

 the railroad bridges, but without a special permit no one is allowed 

 to walk on this roadbed. The contact between the limestone and 

 the shale is here very irregular^ indications of erosion of the shale 

 prior to the deposition of the limestone occurring. The limestone is 

 also somewhat concretionary, rounded masses projecting dowm into 

 the shales. The succession of strata is here as follows: 



1 Concretionary, irregularly bedded gypsiferous limestone, often 

 earthy and with occasional thin, shaly layers; it splits readily into 

 slabs perpendicular to the stratification. Thickness 6-8 feet. 



2 Fine grained limestone with sandy feel, sometimes massive, 

 sometimes in shattered layers with earthy or shaly partings, and 

 separated from the underh^ing rock by an earthy layer. It 

 weathers to an ashy or sometimes an ocjiery color, and varies some- 

 what in thickness. The upper layer is however a solid and fine 

 grained limestone. Thickness 4-4.5 feet. 



Strata i and 2 are the equivalent of the cement beds. 



3 CrystalHne and crinoidal limestone abruptly succeeding the 

 lower bed. It is massive though somewhat thin bedded and con- 

 tains geoditic cavities filled with gypsum. This continues uniform 

 for a thickness of about 19 feet. 



4 Compact limestone ; concretionary with cavities containing gyp- 

 sum and other minerals^ and with sphalerite embedded in the rock. 



