﻿GEOLOGY OF THOUSAND ISLANDS REGION 87 



the two massive beds of Leray limestone which appear in the upper 

 view is absent in most sections, as in plate 20, where the basal 

 Leray bed is the equivalent of the upper bed of plate 22. In addi- 

 tion most of the Lowville shown in plate 22 is absent in other sec- 

 tions, the top Lowville bed in plate 20 being the equivalent of the 

 basal bed of plate 22. 



The Watertown limestone is a solid bank of dark bluish gray to 

 black limestone, with rather indistinct bedding planes, very hard 

 when fresh, showing numerous small caleite crystals (crinoid 

 joints) and a fine reticulation from mud seams and many worm 

 tubes. The mud seams or the earthy intergrowth causes the rock to 

 break up most typically in small blocks. 



When fresh the Leray and Watertown limestones, especially the 

 Seven foot tier, furnish very large blocks. They are for this rea- 

 son still extensively quarried at Chaumont where at present the im- 

 mense blocks required for ^harbor improvements at Oswego and 

 other cities along the Great Lakes are obtained. 



The fact that the 1^-2 feet of black, knotty, impure limestone 

 which overlie the Seven foot tier are separated by a very irregular 

 contact from the overlying horizontally bedded Trenton, indicates 

 that also this bed should be properly included in the Watertown 

 formation. 



The Seven foot tier and the just mentioned top bed of the Water- 

 town formation owe "their deep black color to the grea-t amount of 

 organic matter in the rock. This saturation with organic matter shows 

 itself also in the presence of petroleum in the rock. In the large 

 quarries at Chaumont endoceratites and other cephalopods have 

 been found whose chambers were partly filled with petroleum and 

 the writer was in a cellar in the hotel in Black River village above 

 Watertown that is cut in the Watertown limestone and in which 

 the petroleum is constantly oozing out of the cellar walls m such 

 quantities that the floor is constantly covered with the oil and gal- 

 lons of it are taken out for cleaning and oiling purposes. The top 

 layer of the formation is especially strongly bituminous,- and gives 

 off a strong odor when struck with the hammer. 



The upper beds of the Black River group of the neighborhood of 

 Watertown have become world famous among paleontologists by the 

 fine preservation and slizeof their cephalopods, some of which, notably 

 Gonioceras anceps, have not been found elsewhere. It is 

 essentially a cephalopod f acies. The straight conchs of Hormo- 

 ceras tenuifilum with their large pearly siphuncles, are es- 

 pecially common on the many ice-polished rock surfaces of. the 



