PIKE COUNTY. 25 



three feet of quartzose sandstone resting upon the Niagara limestone, which, 

 no doubt, belongs to the Hamilton group, and is the most northerly outcrop of 

 this formation known in this part of the State. The green and blue shales, 

 sometimes including a few feet of chocolate brown, or black shale, which imme- 

 diately overlies the Niagara limestone here, contains no fossils, and shades into 

 the arenaceous beds of the Kinderhook group so completely, that no line of 

 separation can be seen between them. Hence we have included these shales, 

 which have heretofore been referred to the age of the " Black Slate," of Ohio, 

 in the Lower Carboniferous series, and consider them as probably the equiva- 

 lent of a black shale, that is found in Ohio intercalated in the Waverly sand- 

 stone. This, in the absence of the Hamilton limestone, or any lower division 

 of the Devonian system, leaves the Lower Carboniferous beds resting immedi- 

 ately upon the Upper Silurian limestones. 



A very decided want of conformability may be observed between the Coal 

 Measures, and the limestones on which they rest in this county. Usually in 

 this portion of the State, if the sequence of strata is complete, the Coal Meas- 

 ures rest upon the upper beds of the St. Louis limestone, but this group is 

 wanting here, except on the northern limits of the county, and the Coal Meas- 

 ures are found resting unconformably on the Keokuk limestones, in the east 

 part of the county, and on the Burlington beds, in the western portion. This 

 peculiar feature in the geology of the county, has resulted from the elevation 

 and subsequent denudation of the strata, anterior to the deposit of the coal. 



In addition to the disturbance of the strata, resulting from the Cap au Ores 

 axis, described in the report on Calhoun county, which, no doubt, also affected 

 the strata in the southern part of Pike, there is another, though less decided, 

 axis in this county, which, probably, changed the level of the Lower Carbon- 

 iferous limestones, over nearly the whole extent of the county, and resulted in 

 the subsequent denudation of the strata already alluded to. This axis occurs 

 in the vicinity of Six Mile creek, and its effects are most apparent on the north- 

 west quarter of section 7, township 7 south, range 4 west, where the Niagara 

 limestone rises abruptly from beneath the surface of the bottom lands at the 

 foot of the bluffs, and, dipping north 20 west, at an angle of 7, rises, in a 

 distance of scarcely more than a hundred yards, so as to form a perpendicular 

 cliff, from forty to fifty feet in hight. There has, evidently, been a dislocation 

 of the strata here, for we find this limestone outcropping along the foot of the 

 bluff, from Rockport down nearly to the point where it rises so suddenly from 

 the river bottoms, and showing above this point no very decided inclination. 

 The elevating force, however, was not sufficient to bring the whole thickness of 

 the group above the surface, although about fifty feet in thickness is exposed. 

 The following section will show the thickness of the formations found in this 



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