ROCHESTER AND ONTARIO BEACH QUADRANGLES 23 



5 Thin-bedded dark gray or brownish limestones. Few cavities. 

 Highly bituminous. Sometimes contains nodules of hornstone. 



4 Thick-bedded dark or bluish gray limestone with irregular cavi- 

 ties, and often silicious accretions, or hornstone. Surface very 

 ragged from weathering. Highly bituminous. 



3 A lighter colored subcrystalline mass, very irregularly stratified, 

 contorted and concretionary. 



2 A bluish gray subcrystalline mass, mostly thin-bedded, and 

 separated by seams of dark shale. 



1 Gray or bluish gray silicious limestone ; hydraulic limestone, or 

 beds of passage from the shale below. 



The Allen creek section, while not a continuous one, is favorable 

 for examining the varying characters of this series. The lowest 

 exposure is seen just north from the culvert on the main line of the 

 New York Central Railroad. The outcrops along the creek and at* 

 the Corbett quarry well expose the lower layers of the dolomite. 

 The irregular bedding of some of the lower layers is well shown at 

 the quarry. This exposure continues through the culvert to the 

 south side of the railroad and then follows a covered interval of 

 about 10 feet. The next exposure is seen at Allen creek both above 

 and below the East avenue road. The rock is a very hard dolomite 

 containing a number of cavities. Corals, fragments of crinoids and 

 Strop heodonta profunda have been obtained here. After 

 another covered interval of about 20 feet, an exposure is seen just 

 below where the stream is crossed by the highway. The lower part 

 of the outcrop consists of evenly bedded dolomites, overlain by 

 darker rock containing much Stromatopora. About 2 feet of con- 

 cretionary layers are shown above the dark dolomite. Farther up 

 the stream are 10 feet of dark dolomites with corals, followed by 5 

 feet of hard thin-bedded layers and terminated above by 12 feet of 

 dark brown dolomite containing Stromatopora, Halysites and Favo- 

 sites. This is the highest exposure of the Lockport dolomite on 

 this creek. The next exposure above, which is just south of the road 

 leading to South Park, belongs to the Salina series. 



The following is a condensed section along Allen creek, the 

 thickness of which, as in the above description, is taken from Clarke 

 and Ruedemann. 1 In ascending order: 



FEET 



1 Basal beds of irregular bedded rough dolomites 20 



2 Covered interval 10 



1 N. Y. State Mus. Mem. 5. 1903. p. 18. 



