4 



Utica Slate and 



Having traced the extension of the formation down the Mohawk 

 valley to the Hudson and thence north, north-east, and south-west, 

 we return to Utica and follow it to the north-west across Oneida, 

 Lewis and Jefferson counties to the eastern shore of Lake Ontario. 

 It outcrops on the shore east of Toronto, on the north side of the 

 excavation made in the strata by the lake basin, and, crossing the 

 l)rovince of Ontario in a north-westerly direction, presents a fine ex- 

 posure at Collingvvood on Georgian Bay. With a more westerly 

 trend it is next seen crossing the northern side of Manatoulin Island 

 in Lake Huron, beyond which, in its characteristic black bituminous 

 shaly formation, it has not been traced. 



On Manatoulin Island the thickness has decreased to fifty feet 

 (Logan). 



Dr. C. A. White ' mentions the discovery in black slates in Nevada 

 of Graptolithus quadrimucTonatus^ G. pristis, and two species allied 

 to forms found in the Utica slate. This discovery will have an im- 

 portant bearing on the extension of the Utica epoch to the western 

 side of the continent, should it be substantiated by subsequent inves- 

 tigation. 



Tlx^ Trenton limestone and the strata of the Hudson River for- 

 mation are co -extensive with the geographical range given for the 

 Utica slate. In many instances it is difficult to indicate the line of 

 demarcation between the latter formation and the strata above or 

 below, while in other localities the limits of each formation are 

 clearly defined. In Jefferson county, N. Y., it is only by an arbitrary 

 line that the Utica slate can be separated from the Hudson River 

 formation.- In the town of Deerfield, Oneida county, N. Y., the 

 Trenton and Utica formations are as intimately connected, lithologi- 

 cally, as the Utica formation is with the succeeding Hudson River 

 formation, which is also the case to the north-east on the St. Law- 

 rence ' and in other localities. 



Prof. H. D. Rogers in the Pennsylvania Survey Report, 1858, says: 

 "The transition from the formation of this very fossiliferous 

 limestone (Trenton) to that of the bluish black, carbonaceous, matinal 

 (LUica) shale, was, throughout most of the basin, now accessible to 

 study, somewhat abrupt ; though, as we have seen, it was extremely 

 gradual in one part of their south-east outcrop, or in the northern 

 section of the great valley of Virginia. There, there is such an in- 

 termingling of the materials, and even of the fossils of the two 

 strata, that a division of the blended mass is difficult if not impossible. 



1 Wheeler's Expd. West of the 100th Meridian, iv, Pt. I, Pal., p. 10. 1875. 

 " Emmons's Agriculture of liTew York, i, p. 133. 1846. 

 3 Geology of Canada, p, 202. 1863. 



