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NEW YORK STATE MUSEUM 



road (Direct road), where 20 feet of rough dolomites are shown. The 

 bottom of this exposure is 350 feet A.T. After a covered interval esti- 

 mated at about 10 feet, another exposure (2) is seen at Lincoln's Mills, 

 near the crossing of the East avenue road ; 25 feet of dark bluish gray 

 dolomite, with drusy cavities and showing specimens of Stropheodonta 

 profunda, are exposed. Estimating a covered interval of 20 feet, a third 

 outcrop (3) occurs on the premises of John Balder, consisting of 5 feet of 

 evenly bedded dolomites overlain by 8 to 10 feet of darker rock with 

 Stromatopora. Above are 2 feet of a peculiarly concretionary layer with 

 many corals of the Lockport limestone and similar to a layer in the Pike 

 quarry section, Rochester. Continuous with this exposure, farther up the 

 creek are (4) 10 feet of dark dolomite with corals ; 5 feet of finer, harder 

 and thin bedded rock; 12 feet of dark brown dolomite with Stromatopora, 

 Halysites and Favosites. The summit of the outcrop is about 8 rods east 

 of the Erie canal. Above this section is a covered interval estimated at 

 about 15 feet, and herein probably lies the Guelph horizon of the Nellis 

 quarry, which, as we shall presently note, is above the dolomites in 

 Pike quarry. The exposure next following on the stream (5) is 5 to 6 

 rods long in the low banks and covers about 8 feet of thin " platten" lime- 

 stones of the Salina. In the bottom of the Erie canal, 2 miles north- 

 west of Pittsford, 470 feet A. T., and ^ of a mile from the last named 

 exposure are black shales with interbedded gray " platten " limestones 

 abounding in Salina crustaceans. Exposure 5 has an elevation at the 

 bottom of 485 feet and hence lies above the Salina shales referred to. 

 We may fairly conclude that these Salina black shales lie immediately 

 above the covered Guelph horizon. 



The total thickness of the dolomites here according to the section 

 given, is about 120 feet. 



Brighton. At a rock cut, 1 mile east of Brighton on the Direct road 

 (New York Central Railroad) are 15 feet of brown dolomites with Stroma- 

 topora and Favosites. The exact horizon of this layer in the Lockport 

 dolomites is not altogether clear. 



