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reader, the remarks which follow, on the rock formations of the alove 

 named counties. 



Great difficulty has been experienced in conducting the details of 

 geological examination necessary for arriving at general result's, from the 

 circumstance of the face of our rocks being almost universally covered 

 with a thick mantle of diluvium. This diluvium consists in part of 

 the detritus of the upper portion of our coal series, which has been 

 broken up and washed away, and in part of sands and fragments of 

 the primary rocks, transported from a more northerly region. Owing 

 to this, the rocks of the carboniferous group but seldom make their 

 appearance at the surface ; and the country being little broken by ra- 

 tines or deep water-courses, the outcrop of the rock is not frequent, 

 •Ten where we would be led most to expect it. On this account, I have 

 been compelled to inquire out and examine the deepest wells, and the 

 most important results have been obtained in this rather unsatisfactory 

 manner. This circumstance has not only prevented my defining the 

 variety of rock strata with perfect accuracy, but renders it not improb- 

 able that strata which actually exists in place, were not discovered, in 

 consequence of the thick covering of transported materials. Thus, the 

 rocks which intervene between the great lime-rock formation, and the 

 iron formation of the carboniferous series, (including the shale stratum 

 and sandstones of the Ohio Geologists, and the black slate and lime- 

 stones of Indiana,) are either entirely absent from the southern border 

 of the coal basin of Michigan, or were not visible after the strictest 

 search. 



With this qualifying observation, I shall proceed to a brief descrip- 

 tion of the strata, as far they could be determined, within the district 

 assigned me. 



I. LIMEROCK. 



The limerock of the south-eastern part of the Peninsula, and whose 

 outcrop is seen on the western coast of Lake Erie, is a portion of the 

 great formation described above. Its place is higher in the series than 

 the blue limestone and shales of Cincinnati, but below the black slate, 

 and without doubt is equivalent in position to the " cliff limestone" of 

 Indiana. Inland from the lake the limerock makes outcrops at numer- 

 ous points, which are found to be in distinct ranges, having a direction 



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