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 State an ageregate thick- 
ness of about eight hundred feet, is there divided into three divisions, 
which are named, respectively— 
WL OY L7e WATLOM! DEC Ss = se alu ee a EN UE IAA Seg Sn nota er AR 300 ft. thick. 
he Cincinnati ivisiOne pro pelee reece ee iene sere eee eee Uday GG 
The Point Pleasant beds .......... BA SEALS) RO alte N BUA eo URAC On Aare RT 0). OY 
The Butler county scale begins at about two hundred 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, en the other 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 Orthes retrorsa, Salter—Or- 
this Carley, Hall. This shell is found on the banks of Seven Mile very 
