MACASTEY BLACK SHALE 



693 



upper Chazy, and tlieir first inclination was to refer them to even younger 

 beds — ^that is, to the Lowville and equivalent deposits. Some of the 

 species were then sent to Eaymond, and from what he has seen he is in- 

 clined to correlate the Mingan A3 and A5 zones with the middle Chazy 

 and the "reef fauna at the base of the upper Chazy at Valcour Island, 

 Chazy, and Isle La Motte. Bumastus erastusi and Conocardium beecheri 

 are not abundant there, and all the other species sent me are common at 

 that horizon/' Billings, on the other hand, thought this higher zone of 

 the Mingan series to be of Black Eiver age. 



A larger series was later sent to Ulrich, and as he has collected very 

 similar faunas in widely distributed localities throughout the eastern 

 United States, it was thought that he would find it easy to make definite 

 time correlations. On the contrary^ he found the determination of the 

 ages of the beds in the Mingan series to be a matter of great difficulty. 

 This because "the faunal evidence is on the whole so mixed in its sugges- 

 tions that I question if the problem can be determined satisfactorily at 

 present.'' Ulrich sees no lower Chazy at all in the Mingan series, and he 

 is not even certain that there is any middle Chaz}^ here. He writes : 

 "According to the faunal evidence, the beds containing the A3 biota can 

 not be older than upper Chazy, and it may be a recurrent and modified 

 phase of the north Atlantic fauna in Black Eiver time." As for the white 

 limestone fauna of zone Ag, "it is of Black Eiver age, and probably repre- 

 sents a late rather than an early stage of that group. It is clearly a later 

 phase of the A3 fauna with the addition of the mollusca, which commonly 

 go with such a rock." 



For the present the Mingan zones A^ to A3 are tentatively correlated 

 with the upper Chazy of ^N'ew York, and A5 with the earlier stages of the 

 Black Eiver. Accordingly, zone A^ holds the horizon of the Lowville of 

 New York. 



Anticosti Island Succession 



ordovigig system. magaste7 black shale 



Location and characteristics. — Along the northwest end of Anticosti 

 from English Head east to Macastey Bay the sea throws up a black shale. 

 At the latter place the junior author in 1909 found considerable quan- 

 tities of this shale along the beach, and in a few places large blocks, par- 

 ticularly at Macastey Mountain, indicating that these deposits are in the 

 immediate shallow water outside the reef fringing the island here. This 

 occurrence has added value, in that it indicates that the Anticosti strata 

 of Eichmondian time repose directly on these black shales. In regard to 



XLVIII— Bull. Geol. Soc. Am., Vol. 21, 1909 



