HURON COUNTY. 



305 



Broken Strata of Erie and Bedford Shales. 



iilA> OF blRllAM 



The mass of the bluff is of Erie shale, with the hard bands which it 

 contains broken up and tilted, but not removed from their connection 

 with the including strata with which they are slill in contact. The irreg- 

 ular masses BB are "turtle-backs" of the Bedford shales buried in the 

 mass of the Erie. 



All these outcrops of rock occupy now substantially the same topo- 

 graphical level. The Erie shales alone are in their original beds. All 

 the others have been disturbed and tilted, pushed out of their beds, and 

 carried to a lower level by the ice. 



In the immediate neighborhood, the Berea is exposed in several places 

 dipping in various directions, and varying from 20° to 40°. These dis- 

 turbances have left the Berea here resting on the Cleveland shales, and 

 have so broken up and crushed the strata as to greatly impair the value 

 of the quarries in the county. In a few places, even where the rock is 

 tilted up to quite a sharp angle, the strata are still entire, and excellent 

 rock can be quarried. At many of the openings, the broken, worthless 

 rock largely exceeds that which is suitable for building purposes. 



BEDFORD SHALES. 



The section on page 303 exhibits the general character of the Bedford 

 shales in this county. They are exposed only in the difftirent branches 

 of the Huron and Vermillion Rivers. Where undisturbed, they range 

 from forty to seventy-five feet in thickness, and consist of hard, fine- 

 grained sand-rock in their layers, alternating with thinner bands of 

 argillaceous shales ; the thicker strata of the sand-rock are frequently com- 

 posed of a mass of the peculiar contorted rock called " turtle-back," ren- 

 dering it quite worthless. Sometimes, however, this formation yields a 

 fair building stone. In places where quite a heavy bed of the Berea con- 

 stitutes the surface rock, these shales are entirely wanting, the Berea 

 resting upon the Cleveland shales. 



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