570 



Report of the State Geologist. 



the Chazy, and is missing from Brainard and Seely's section. The rock is 

 very like No. 3 of Division C, of that section. 



Trenton limestone. North and east from Chazy village, the lower portion 

 of the Trenton is found exposed, a thickness of about 150 feet being shown. 

 The best section is that in the Little Chazy river, just east of the village, 

 w here the dip is high, so that w ithin a short interval, a considerable thickness 

 of the rock is exposed. Alternating beds of black, rather slaty limestone, 

 and more crystalline beds of lighter color, which are full of brachiopods, 

 make up the section. They are in all respects similar to the lower beds on 

 Crab island and in Plattsburgh, but here in Chazy is the only locality found 

 in the county w here the Black river and Chazy limestones may be seen in 

 place below them. 



Faults. Owing to the better and more frequent exposures, the faults 

 which have dislocated the Palaeozoic rocks are more readily worked out in 

 detail in Chazy than elsewhere in the county. They have already been 

 discussed by the writer, in so far as the stage of the work would permit.* 

 The past season's work in company with Messrs. Van Ingen and White 

 corrected • inaccuracies in two instances, and later on some other errors were 

 found. 



The most conspicuous and important break shown in the vicinity, is the 

 great fault running across the township from southwest to northeast, and on 

 into Champlain township. It will be called the Tracy brook fault, as the 

 entire course of that stream lies along the fault line. Along its course 

 through Chazy the entire Calciferous is blotted out, the various members of 

 the Chazy and even of the Black river being brought down against the 

 Potsdam. The entire throw is not far from 2,000 feet. 



The downthrow block on the east of this fault is much shattered, and 

 consists of a series of small blocks caused by cross faults. The dip is steep, 

 ten degrees or more, and the amount of throw is ordinarily to be determined 

 with ease by the surface shift of the Black river limestone, which forms the 

 most convenient horizon for this purpose. Seven of these cross faults have 

 been identified in a distance of three miles, and doubtless others will be dis- 

 closed, as detailed mapping is extended southward. This shattered zone is 

 terminated eastward by another fault, which closely follows the course of the 

 Little Chazy river, and may therefore be called the Little Chazy fault. But 

 to the north and south it passes into drift-covered territory, beyond w hich 

 it can not be traced. East of this fault is the long continuous section 



* Bulletin Geological Society of America, Vol. VI , pp. 285-296. 



