HURON" COUNTY, 



303 



For a few rods below this exposure the bed of the stream and bluffs are 

 composed of Drift, mainly the debris of local rocks, the first rock seen 

 beyond being that mentioned above, inclined at an angle of 75°, and 

 standing like a dike directly across the bed of the stream. 



The character of the Drift banks is indicated by the following section 

 of the blufif at this dike : 



Yellow clay and gravel 8 to 12 



Blue clay and gravel. 



12 



Debris of the "turtle-back" rock with Drift pebbles. 



This "turtle-back," or. pudding rock, is a very peculiar formation, 

 composed of a mass of indurated mud-balls, sharply separated from the 

 including strata with the internal structure of the slag of a smelting fur- 

 nace. If a mass of thoroughly worked, tenacious clay could be slowly 

 pushed forward over a gentle slope, constantly folding upon itself in the 

 manner in which the slag flows from a furnace, a structure very similar 

 to that found in these strata would be produced. Studied at this point 

 alone, where their peculiarities are the most marked, an explanation of 

 the mode of their formation is very difficult.* 



Following the stream still further downwards, the rock disappears both 

 from the bed and blufls of the stream, first reappearing near the little 

 village of Maxville. where it has a slight dip to the north which soon in- 

 creases to 19°. A little north of this, after passing a fissure in the rock, 

 the dip is 13J° north 60° west. Still further north, near the west line of 

 Bronson township, a rock exposure at the bridge, over Huron River, ex- 

 hibits another phase of this general disturbance. 



The following is a profile of part of the exposure : 



A — Sandstone of Bedford shales. 



E — Cleveland shales. 



C — Claj and debris of Erie shales. 



* In the valley of the Cuyahoga, on the same horizon, the rocks exhibit a slight ap- 

 I>roaoh to this structure, and it is there apparently due to sea weeds. It would seem 

 that in this locality a mass of fucoid plants, rolled and tumbled by the waves, were 

 spread upon the surface and buried under a deposit of clay and sand, which, when har- 

 dened into rock, has retained the irregular, distorted, internal structure thus given to it. 



