

1854.] 



PHYSICAL STRUCTURE OF THE WESTEBN DISTRICT OF UPPER CANADA. 



%\t. Canaltrkit |0itrnaL 



TORONTO, AUGUST, 1854. 



On the Physical Structure of the Western District of 

 Upper Canada. 



By W. E. LoGAS, F.R.S., F.G.S., and Director of the Geological 

 Survey of Canada. 



The Western District of Upper Canada has, at a short distance 

 on the north-west side of it, the coal-field of Michigan, and at 

 a somewhat greater on the south-east, what has been called the 

 coal-field of Appalachia. The former, as has been ascertained 

 by the investigations of the geologists of the United States, 

 occupies the chief part of the interior of the southern peninsula 

 of Michigan, and has a superficies of about 12,000 square miles, 

 while the latter, extending in length from the north-eastern 

 corner of Pennsylvania to Tennessee, and in breadth from the 

 vicinity of Lake Erie to the sources of the Potomac, presents 

 the greatest known carboniferous area on the face of the globe, 

 its surface being e(jual to about 60,000 square miles. The 

 rocks of the Jlichigan coal-field, where they approach nearest 

 to Lake St. Clair, and those of the Appalachian, where they 

 do the same in regard to Lake Erie, exhibit an attitude so near 

 to horizontality, that, without accurate admeasurements, it would 

 not be easy to detect their dip. Those between the coal-fields 

 and the two Lakes equally do so, and those again between the 

 Lakes themselves are, as a whole, flatter still. The Western 

 District, thus flanked on both sides by coal measures, and show- 

 ing no easily observed reason in the dip why they should not be 

 carried across it, might induce those who had made no careful 

 examination of the matter to entertain a hope that some out- 

 Ij'ing patch of such measures might yet be found in that part 

 of Canada. The ascertained structure of the District, however, 

 shows that such a hope would be ill founded ; and I propose 

 to place before the Institute an explanation of what that stnic- 

 ture is, illustrated by a map and section, that part of the 

 map representing a portion of the United States being copied 

 from the works of American geologists. 



The rocks comprehended in the section in descending order 

 are — 



1. GneissoicT, or Metamorphic series. 



2. Huronian, or Copper-bearmg rocks, perhaps equivalent to the 



Cambrian of England. 



3. Potsilam Sandstone. 



4. Calciferous Sand-rock, Chazy, BirJscyo, Black River, 



and Trenton Limestones. 



5. Utiea Slates. 



6. Hudson River gi-oup. 



7. Medina Sandstone. 



8. Clinton and Niagara groups. "| 



9. Gypsiferous Rocks, or Onondaga Salt group. [-Upper Silurian. 

 10. Corniferous Limestone.* J 



* What is called the Corniferous limestone, under No. 10, is intended 

 to represent whatever there may bo in Canada of those deposits which, 

 in tlie New York series of rocks, compose the Ilelderberg series, with 

 the exclusion of the Onondaga Salt group ; and, it may bo liero 

 remarked, that the line of division between the Upper Silurian and 

 Devonian rocks is given as merely approximative. The true position 

 of this line seems as yet not quite certjiin, but it is supposed to bo 

 some where about the middle of that portion of tho Ilelderberg series, 

 which lies above the Onondaga Salt gi'oup. 



Vol. III., No. 1, Aboust, 1854. 



Lower 

 Silurian. 



11. Hamilton group. "I Devonian 



li!. Chemvmg and Portage groups. J 



13. Mountain or Carboniferous Limestone. I ^.^^^^j^^^^^^ 



14. Coal measures. J 



It is not my intention to give any detailed description of 

 these rocks, but for their mineral and fossil contents, as well 

 as their respective thicknesses, refer to the various ofiicial 

 reports presented to the government on the progress of the 

 geological suney of the Province, and those of the geologists 

 of the United States ; nor shall I allude to their geographical 

 distribution in detail farther than as occasion may require, the 

 map being sufEoient to explain it. 



Taking these rocks in their general groupings, it will be 

 perceived by the map that the Lower Silurian series, by a 

 change in the strike from west to north-west, sweeps round 

 from Lake Ontario to Georgian Bay, and proceeds thence by 

 the north side of the Manitoulin Islands, and the north shore 

 of Lake Huron, to tho northern peninsula of Michigan, gradu- 

 ally curving to Green Bay, in J^ake Michigan. The Ujiper 

 Silurian follows them. The Niagara Limestone at the base 

 aids in forming the neck of land separating and holding up 

 Lake Erie from Lake Ontario, and continues in a ridge along 

 the Blue Mountains, and the promontory terminating at Cabot's 

 Head and Cape Hurd, of which promontory the chain of the 

 Manitoulin Islands is only an interrupted prolongation. The 

 Gypsiferous rocks succeed conformably, niuning from Grand 

 Island, by the AVelland and Grand Elvers, to the River Sanguine, 

 while the superimposed Corniferous Limestone, from Lake Erie 

 on the one side and Lake Huron on the other, is projected for- 

 ward into the Western District as far as the Township of Zone. 

 The same formation, with a projected form in an opposite direc- 

 tion, comes up from Ohio by the upper end of Lake Erie, and 

 is carried north-easterly as far as the eastward side of Chatham. 

 Between Zone and Chatham, the Hamilton group, composed 

 of blaek bituminous shales, constitutes a narrow band, which 

 runs north-westward towards Lakes Huron and St. C'laii-, and 

 south-eastward to Lake Erie, gradually widening in both direc- 

 tions in the surface it occupies, and finally merging into two 

 rings, or irregular circular belts, one of which is i-udely con- 

 centric with the coal measures of Michigan, and the other with 

 those of the Appalachian field — of which last, however, the 

 luap shows but a small portion. Within these two rings, thus 

 united by the band across the Western District, and between 

 them anil the carboniferous centres, the Chemung and Portage 

 groups occupy their place, in two broad and entirely separate 

 zones, one of them showing itself north-west of Lake St. Clair, 

 and the other south- cast of Lake Erie. 



To any one accustomed to consider tho forms derived from 

 the intersection of surfaces, who will carry in his mind tliat the 

 various formations wliich have been given are nothing more 

 than a set of thick, close-fitting, conformable sheets, which are 

 intersected by the general surlkce of the country, it will be at 

 once apparent that the ascertained geographical distribution of 

 the formations results from the fact that between the Michigan 

 and Appalachian coal-fields there is a flat anticlinal arch, the 

 axis of which runs, with a gentle curve, from the upper extremity 

 of Lake Ont;irio by London, Zone, and Maiden, to the Mnumd 

 River, at the upper end of Lake Erie, and that between Chatham 

 and Zone there 19 in it a slight transverse depre,s,sion. Tliis 

 anticlinal arch is represented in the section, the line of which 

 runs in a north-west and south-east direction from the one 

 coal-field to the other, a little south-west of tho naniilton 

 shales in Chatham. The section is given on a scale of one 



