MIDDLE AND UPPER OEDOVICIAN. 209 



The last of these subfaunas shows evidence of a transition into the Utica-Lorraine grapto- 

 litic fauna of the Mohawk Valley, New York, and of Lake St. John, Canada. 



Ulrich states that the fauna may be called Trentonian only if that term is used 

 as a synonym of Mohawkian and that the so-called Normans Kill is as old as the 

 Black River. 



The stratigraphic succession and structural relations are involved in the over- 

 thrusts of the sedimentary strata, and the distribution is probably not so simple as 

 it appears even on the detailed maps. The horizon of the Marsouin River formation 

 is repeatedly referred to by Ells ^^°^' ^"''' ^^^^ in tracing the sweep of Ordovician 

 strata through the "Eastern Townships" of Quebec, the similarity of the rocks and 

 graptolites indicating the continuity of the zone of deposition as far as the locality 

 of the Magog shales on Lake Memphremagog. In Vermont and New Hampshire 

 the terrane is probably represented in the metamorphosed Paleozoic rocks. 



M 20. MINGAN AND ANTICOSTI ISLANDS. 



Ordovician strata are exposed along the north coast of Anticosti Island, dipping 

 gently southward under the Anticosti group (Silurian). The lowest strata seen 

 at the base of the cliffs are assigned by Logan to the "Hudson River" [Richmond] 

 formation. Farther north, across the strait, the Mingan Islands consist of rocks 

 referred to the " Calcif erous " (Beekmantown) and Chazy, with possibly part of 

 the "Birdseye" (Lowville) and Black River formations. The closely adjacent 

 coast of Quebec is " Laurentian. " Thus it appears that the middle Ordovician 

 strata in this region overlap the earlier Paleozoic (pre-Beekmantown) rocks and 

 extend from the north margin of the Gulf of St. Lawrence southward beneath its 

 waters to Anticosti, where the overlying upper Ordovician and Silurian are exposed. 



Regarding the Chazy of the Mingan Islands, Logan ^**^ says : 



At the Mingan Islands the Chazy formation bears lithological characters somewhat different 

 from those which have been given above. The lowest part seen of the deposit occurs in the 

 bay above Clear Water Point, and the following is a section of the strata in ascending order: 



Feet. 

 Reddish cream-colored compact limeatone with a conchoidal fractm'e, weathering pale yellow. . 1 



Greenish and brownish-black shale 1 



Reddish cream-colored limestone as before, in beds of from 1 to 2 inches to a foot, interstratified 



with greenish shale in beds of about the same thickness 28 



Greenish shale with Khynchonella orientalis (which is a variety of R. plena) in great abundance. . 3 

 Gray granular limestone with false bedding, holding comminuted fragments of encrinites and 

 other organic remains, including Bolboporites americanits, Ehynchonella orientalis, a few of 



Camerella longirostrata, and other species 13 



Gray nodular limestone with Columnaria parva, Stenopora adherens, Fenestella incepta, Orthis 

 piger, Strophomena incrassata, Ctenodonta nasuta, Nautilus jason, Amphion canadensis, Harpes 



antiquatus, Illsenus globosus 20 



Gray magnesian limestone, with Murchisonia aspera, Maclurea atlantica, Orthocerasmulticameratum, 

 0. bilineatum, 0. natator, 0. maro, 0. antenor', 0. minganese, 0. shumardi, lUxnus hayfieldi, and 

 other fossils 12 



78 



Apparently above these strata but not in immediate sequence Logan lists gray 

 and yellow limestone and green shale in thin beds to a thickness of 171 feet, almost 

 without fossils, which he, however, regards as Chazy and possibly not including 

 the top of that terrane. Ukich suggests that these strata may be Lowville. Above 



48011°— 12 14 



