Parking: N39° 1.605 W84° 30.576
The Mason Road road-cut is an outstanding and easily accessible
exposure of Upper Ordovician strata known as the “Cincinnatian
Series.” Four lithographic units are exposed at the site: The Kope
Formation, the Fairview Formation, the Bellevue Limestone, and the
Miamitown Shale. Only the Kope and Fairview formations are easily
accessed; the Bellevue Limestone and Miamitown Shale are near the
top of the exposure, and are difficult to reach.
The Kope Formation is over 200 feet thick at the site, although
only the upper 28 feet is exposed. The Kope Formation is composed
of interbedded limestone, siltstone, and shale, with shale
comprising about three-fourths of the total thickness. The most
common fossils are small (dime-sized) brachiopods and bryozoans.
Crinoid and trilobite fragments, and other trace fossils have also
been reported.
Above the Kope Formation is 104 feet of the Fairview Formation.
The exact border between these two layers is difficult to identify.
Like the Kope Formation, the Fairview Formation is composed of
interbedded limestone, siltstone, and shale, but unlike the Kope
Formation, the Fairview Formation is about 50% limestone. The most
common fossils are brachiopods, bryozoans, and crinoids. The
brachiopods tend to be larger than in the Kope Formation (up to 2
inches across), and the crinoids far more abundant. Some small
gastropods (under 1 inch) are also found, but not in abundance.
Pelecypods, trilobite fragments, cephalopods, and other trace
fossils have also been reported.
Above the Fairview formation, but not easily accessible, is a
16-foot thick layer of Belleview Limestone, and a 1.3-foot thick
layer of Miamitown Shale.
Text adapted from: Davis, R.A., Cincinnati region: Ordovician
statigraphy near the southwest corner of Ohio, Geological
Society of America Centennial Field Guide - Southeastern
Section, 1986.