NIAGARA FALLS AND VICINITY I05 



Upper shales. Above the Bryozoan beds the shale is soft, and 

 more evenly and finely laminated, splitting often into thin slabs of 

 moderate size. Hard calcareous beds are generally absent, though 

 occasionally found near the top. The stratification and lamination 

 is much more strongly marked in this than in any other division of 

 this rock. When freshly broken, the shale has a brownish earthy 

 color, which changes to grayish when the rock decomposes to clay. 

 Fossils are rare, those found being seldom well preserved. In most 

 cases the shells are dissolved away, leaving only the impressions of 

 the fossil, which from compression become faint, and are not readily 

 recognized without careful scrutiny. The most common remains 

 found in these rocks are bivalve mollusks (pelecypods) and tri- 

 lobites. Among the former Pterinaea em ace rat a is 

 the most abundant, while D a 1 m a n i t e s limulurus is the 

 chief among the trilobites of these beds. Other trilobites also occur 

 in these shales, notably Homalonotus delphinocepha- 

 1 u s , as well as a number of brachiopods. 



Toward the top fossils become rarer, and finally are wanting al- 

 together. The shale becomes more heavy bedded, and calcareous 

 layers begin to increase. The last 10 feet or more are quite calcare- 

 ous and compact, and have an irregular fracture. They grade up- 

 ward into the basal layers of the Lockport (Niagara) limestone. 



Lockport (Niagara) limestone 



The limestone which succeeds the Rochester or Niagara shales 

 forms the summit rock of the series from the edge of the* Niagara 

 escarpment to south of the falls. It consists of a number of dis- 

 tinct strata, of varying characters, most of them very poor in organic 

 remains. The total thickness exposed in the Niagara region is not 

 over 130 feet, but borings show that the thickness of the limestone 

 lying between the Rochester shale and the Salina shales is from 200 

 to nearly 250 feet. Some of the upper beds of this limestone mass 

 may represent the Guelph dolomite and others may belong to the 

 base of the Salina beds. Nevertheless we may confidently assume 

 that the thickness of the Lockport limestone in this region, is at 

 least 150 feet. 



