[ells] palaeozoic outliers IN THE OTTAWA RIVER BASIN 143 



coloured, bituminous and compact, with partings of dark brown or black 

 argillaceous shale. This formation is particularly rich in organic remains, 

 both of corals, shells and trilobites, and the area between the Ottawa and 

 St. Lawrence, occuj^ied by it, is estimated at over 000 square miles. The 

 total thickness of this foi-mation as developed in the loAver Ottawa basin 

 is not far from 650 to 700 feet. 



The Utica and Hudson River (Lorraine) formations constitute the 

 upper members of the Camln'o-Silurian system. While having their 

 greatest development in the St. Lawrence valle}', they also appear at 

 several points in the Ottawa basin. The rocks of the lower division, or 

 the Utica, are usually black brittle bituminous shales with thin bands of 

 yellow-weathering limestone. The foi-mation is thus lithologicall}" distinct 

 from the underlying Trenton. The thickness as given in the typical 

 section at the Montmorency Falls, below (-Quebec, is 818 feet, l)ut this 

 thickness must be greatly reduced for the deposits in the Ottawa basin 

 where it will probabl}' not reach one hundred feet. There is no detined 

 break between the strata of the Utica and those of the Lorraine, the 

 passage being apparently conliniious, through the replacement of the 

 dark bituminous beds by grayish shales and sandstones and by an almost 

 entire disappearance ot calcareous matter. The thickness of the up])er 

 division is placed at 719 feet in the St. liawrence section, but as in the 

 case of tlie Utica this must be also vary largely reduced for the western 

 area. The only known outlier of the Lorraine to the sovitheast of Ottawa 

 is represented by a very thin series of beds, probably not more than thirty 

 or forty feet in so far as yet observed. 



The formations just described for the lower Ottawa area complete the 

 Cambro-Silurian series ; but as already intimated, in the townships 6f 

 Osgoode and Russell, certain reddish shales and sandstones' occur which 

 overlie the Lorraine, and ])resumably represent the Medina division of the 

 Silurian. No fossils have yet been found in these newest outliers : and 

 owing to the great mantle of drift with which they are surrounded, and 

 for the most part concealed, their thickness cannot be ascertained. 



In order to complete the series of Palaeozoic formations which occur 

 in the area now" being discussed we may here refer to the peculiar outlier 

 of Niagara rocks which occurs near the upper end of Lake Temiscaraing. 

 A description of these is given in the Geology of Canada, 1863, from 

 which we learn that the formation lies unconformabl}' upon the sand- 

 stones (quartzites) of the Huronian of that district. The lower part of 

 the outlier is generally arenaceous, and very often a conglomerate, con- 

 taining large boulders of the underlying rock. Mr. A. E. Barlow, who 

 has recently studied these rocks, describes them as occurring on both 

 sides of the lake as well as on Chief's Island and on several smaller islands 

 near b3\ The base of the deposits is said to '■'■ consist of vast boulders and 



1 Geology of Canada, 1863, p. 219. 



