400 GEOLOGY OF OHIO. 



or Cincinnati Group of Ohio. The exception named above is found 

 in the north-eastern corner of Oxford township, where a spur of the 

 Cliff Limestone crosses the county line, and covers a section or two of 

 the county. Dr. Locke called attention to this spur in the report of 

 the former State Survey. Both the Clinton and Niagara formations 

 are shown here, but the area is so small, and is known to so few resi- 

 dents of the county, comparatively, that it will be dismissed from fur- 

 ther consideration at this time. 



The general geology of the Cincinnati Group has been treated at 

 length in Chapter XIII. of Vol. I. of the Final Report of the Ohio 

 Geological Survey. This chapter may be taken as a part of the report 

 on the geology of Butler county. To it the reader is referred for the 

 general considerations upon the origin and history of this most interest- 

 ing formation. The series, which has in the ^tate an aggregate thick- 

 ness of a.bout eight hundred feet, is there dividtd into three divisions, 

 which are named, respectively — 



The Lebanon beds 300 ft. thick. 



The Cincinnati division proper 425 " 



The Point Pleasant beds 50 " 



The Butler county scale begins at about tvvo hu^idred feet above the 

 base of the system, and extends to the summit of the series. It thus con- 

 tains about six hundred feet of bedded rocks — or, in other words, com- 

 prises somewhat more than one-half of the Cincinnati division proper, 

 and the whole of the Lebanon division. 



There are few peculiarities of stratification or fossil- contents in the 

 county that deserve special mention here; and, on the othep hand, 

 there are few points of interest in the formation at large that are not 

 shown in Butler county. It is emphatically a Blue Limestone county, 

 its bedded rocks belonging almost entirely to this series, and its drift 

 being also largely referrible to it, while its topography, its soils, and 

 its water-supply are all controlled in considerable part by this formation. 



One of the best sections in the county can be found at and near 

 Hamilton. In the quarries just west of the river, the section can be 

 begun at a horizon about two hundred and seventy-five feet above low- 

 water at Cincinnati, and it can be followed in frequent outcrops to the 

 summit of Heitsmann's Hill, on the Millville pike, where many of the 

 characteristic fossils of the Lebanon division are found. 



The streams in the vicinity of Oxford, Seven Mile, and its tributaries, 

 furnish very prolific although not very extended exposures. The hori-" 

 zon is quite definitely fixed by the presence of Orthis retrorsa, Salter — Or- 

 this Carleyi, Hall. This shell is found on the banks of Seven Mile very 



