630 REPORT— 181)7, 



It is not distinctly stated that No. 3 rests unconformably on the older rocks, 

 iDut the observation that granitic boulders were found in it, leads to the belief 

 that such unconformity was assumed. Murray, however, supposed the junction 

 as seen on the Kaministiquia to be conformable, and unites the first three subdivi- 

 sions, as above given, in one series. 



Logan further states, still referring to the same region, that the ' chloritic 

 slates [schists! at the summit of the older rocks on which the volcanic formations 

 rest unconformably, bear a strong resemblance to those met with on the upper 

 part of Lake Temiscaming on the Ottawa, and it appears probable that they will 

 be found to be identical.' 



It will thus be observed that the progress in classification made, up to this date 

 at least, entirely accords with the results of the latest investigations. The identity 

 of the rocks placed third in the table with those of the Upper Ottawa was 

 more than conjectured, and the existence of a great stratigraphical break at the 

 base of what is now known as the Animikie was clearly recognised. The several 

 formations were merely described. No specific names were given to them at this 

 time by Logan, and it is further stated that the age of the highest formations 

 (Animikie and Keweenawan) was in doubt, although some reason was found to 

 support Houghton's* view (or what was believed to be his view), that these 

 formations are lower than the Potsdam, or ' lowest fossiliferous formation.' 



In 1847 and 1848, investigations were continued along the north shore of Lake 

 Huron, of which the characteristic rocks are, it is stated, believed to form a single 

 .system. They are described as in part sedimentary (quartzites, conglomerates,^ 

 &c.), and in part igneous (greenstones), the latter being both interposed between 

 the sedimentary beds and intrusive. The ' slates ' are particularly characterised 

 by Murray as often chloritic, epidotic, and micaceous, and would now, of course;^ 

 be more specifically termed schists. 



Writing in 1849,- however, and later, in a communication presented to this 

 Association in 1851, Logan, although still recognising the manifest unconformity 

 at the base of the Animikie, speaks collectively of the ' Copper-bearing Ilocks ' of 

 Lake Superior and Huron, including imder this general term what are now known 

 as the fluronian, Animikie, and Keweenawan series, and adds that it is ' highly 

 probable ' that all these are approximately equivalent to each other, and to the 

 Cambrian of the British Islands. 



In the Report for 185:2-o3 (published 1854), the name Laurentian was adopted 

 for what had been previously designated merely as the ' metamorphic series,' and 

 in the geological sketch printed in Paris in connection with the Exhibition of 

 1855 (which follows next in order of publication), this system is stated to consist 

 almost exclusively of much altered and disturbed sedimentary beds. It is also, 

 however, made to include some recognised intrusives, such as granite and syenites, 

 forming parts of the mass, as well as the Labradorite rocks, which were after- 

 wards for a time named Upper Laurentian, and to which further allusion will 

 be made in the sequel. The name Laurentian is here therefore first employed 

 exactly in the sense of the term 'Basement Complex,' introduced long afterwards, 

 but under the distinct idea that most of the rocks are altered sediments, from 

 which certain intrusive masses were not clearly separable. 



In the same publication, the overlying series of Lakes Huron and Superior, 

 including the Iluronian proper, the Animikie and the Keweenawan, were collec- 

 tively spoken of as the 'Huronian or Cambrian system.' These rocks are 

 described as lying discordantly on the Laurentian, and as intervening between it 

 and the lowest known fossiliferous strata. There being no other recognised place 

 for such rocks in the scheme of the day, they are consequently supposed to- 

 represent the Lower Cambrian of Sedgwick. 



It is unnecessary to follow in order the investigations carried on for a number 

 of subsequent years, but reference may now be made to the ' Geology of Canada,' 

 of 1863, in which all previous results of the Survey to that date were collected and 



' Then State Geologist of Michigan. 



* Heport on the North Shore of Lake Huron, 



