MICHIGAN ACADEMY OF SCIENCE. 



177 



THE GEOLOGICAL CONTINUITY OF ESSEX AND KENT COUN- 

 TIES, ONTARIO, AND MONROE AND WAYNE COUN- 

 TIES, MICHIGAN. 



Rev. Thomas Nattress. 



When requested by the secretary of the Geological Department of the 

 Academy, and at the instigation of the State Geologist of Michigan, to pre- 

 pare a paper to be read here, I recognized in the request a challenge to solve 

 a problem. That problem is to explain the presence, elevation, dip, and 

 nature of the outcrop of the Corniferous (*or Dundee) in the Amherstburg 

 Quarries, in Anderdon Township, Essex county, Ontario. According to 

 the ascertained lines of outcrop of Silurian strata on the Michigan side of 

 Detroit river at its mouth, the same Silurian surface extension would be 

 looked for in the Southern half of Essex. But it isn't there — except in the 

 river bed, and northward of Lime Kiln Crossing ashore. In its place is an 

 outcrop of Corniferous, with southwesterly dip at the Amherstburg Quarries, 

 and maximum elevation of 609 feet. The successive lines of outcrop in 

 Ontario and Michigan, concentric in the coal area of Michigan, would lead 

 one to expect a north to northwesterly dip. But the natural expectation 

 is denied by the contrary fact. 



The several strata, from the bottom of the high grade limestone deposit 

 which lies immediately upon a brown dolomite, up through the heavy-bed- 

 ded rock, to the surface of the thin-bedded limestone, thin out to nothing, 

 as illustrated in the accompanying diagram by the heavy 10 ft. bed DD'. 



C.-v*A*^t 



Stta^it » 



•5*-^- 



From A to B in the diagram is drift. From B to E is a Devonian rock 

 surface. From E northward the rock (which is Silurian) falls away rapidly, 

 until at A', less than forty rods away, it is 50 feet down, a depth of drift 

 that is fairly uniform over a large area of the middle western part of the 

 county. There may be a fault in the Silurian here. But, if so, it would ex- 

 plain nothing in regard to the Devonian outcrop. *?l 



The evidence goes to prove a Silurian anticlinal, northward of the De- 

 vonian deposit in Anderdon, upon which the Corniferous strata have been 

 deposited with south to southwesterly dip. 



* The Dundee of Monroe county, as described by Professor Sherzer (Geological Report 

 on Monroe County, Vol. VII, p. 1, Geological Survey of Michigan, 1900), is essentially a 

 high grade limestone; whereas, in the Amherstburg quarries there are three several de- 

 posits, the lower averaging 97.5 Ca Co^, the middle about 60.9, and the upper 80.+ (See 

 Bureau of Mines, Ontario, 1904, Vol. ll, "The Limestones of Ontario.) 



