296 E. BRAINERD — THE CHAZY. FORMATION. 



Thickness. 



4. Dark, compact, fine-grained limestone, with obscure bedding, 



weathering to a light gray. This rock resists erosion, and 

 is the upper stratum at Bluff Point, sloping upward from 

 the lake at an angle of 5° to a height of 170 feet. In one 

 exposure the basal portion is densely oolitic. Fossils are 

 infrequent, but at a single locality there were collected 

 Orthis perveta, Con. ; Ortliis platys, Bill. ; Lepkena fasciata, 

 Hall; Asaphus canalis, Con.; C heir urns polydorus, Bill.; 

 Harpes sp. und. ; Illcenus incertus, Bill. ; Lichas mingan- 

 ensis, Bill. ; Splicer exochus parvus, Bill. ; and several uude- 

 scribed species . . . . . .20 feet. 



5. Bluish-black limestone like number 3, but less pure, containing 



Maclurea magna, Leseuer ; Orthis perveta. Con, ; Strophomena 

 incrassata, Hall ; Orthis borealis, Bill. (?) ; Orthis disparilis, 

 Con., or 0. porcia, Bill. . . . . .75 feet. 



Total thickness of J5 . . . . .350 feet. 



Group C (Upper Chazy). 



1. Dove-colored compact limestone, in massive beds, containing a 



large species of Orthoceras ; Placoparia ( Calymene) multi- 



costata, Hall; Solenopora compacta; and a \'^iVgQ Bucania . 60 feet. 



2. Dark impure limestone, in thin beds, abounding in Rhynchonella 



plena; at the base a bed 4 or 5 feet thick is filled with vari- 

 ous forms of J/o?i^icit/ipora or >S'^e>iojoora . . . 125 feet. 



3. Tough, arenaceous magnesian limestone, passing into fine- 



grained sandstone . . . . . .17 feet. 



Total thickness of C . . . . .202 feet. 



Aggregate thickness of the Chazy on Valcour island, 890 feet. 



Chazy Section. — Eighteen miles north of Valcour island is the village of 

 Chazy, from which the formation was named. We published an account of 

 "the original Chazy rocks," with a map, in the American Geologist for 

 November, 1888. The section is almost a repetition of the Valcour section^ 

 and we shall briefly note only some peculiar features. 



It should be stated that the original Chazy, as defined by Emmons, was 

 only what we have called Middle Chazy, or the portion characterized by the 

 presence of Maclurea magna. The strata of Group A he placed in the 

 Calciferous formation, though he recognized that they were higher than 

 the strata elsewhere called Calciferous. The strata of Group C he classed 

 with the Birdseye, as a peculiar development underlying the ordinary Birds- 

 eye. But Professor Hall four years later described the fossils of both these 

 groups as belonging to the Chazy, and this view has been universally 

 accepted. 



