CLINTON CONGLOMERATES AND WAVE MARKS. 189 
The dlack slate covered all regions of Kentucky where proper 
horizons are exposed at present. 
Mention has already been made of the iron pebbles just 
beneath the heavy beds of the Niagara in western Washington 
county, and of the rounded grains of quartz above the Crab 
Orchard shale in Garrard county. In the geology of Lincoln 
county the statement is made that in nearly all the layers of the 
Upper Silurian and Devonian, and even in the base of the black 
slate, there are small transparent grains of quartz. These are 
nearly microscopic but they are well rounded. In the black 
slate they are mentioned from Nelson, Lincoln, Garrard and Clark 
counties. Wave marks occur in the black slate in Lincoln 
county and also in Clark county, near the base. 
Unconformities—In southern Clinton county and adjacent 
Tennessee the black slate rests directly upon the Hudson River 
rocks. In the northern parts of the county, and in Cumberland 
county, it rests upon the Cumberland sandstone. In Lincoln 
county both the Corniferous and the Oriskany appear below the 
black slate, but the Oriskany rests sometimes upon the Crab 
Orchard shale and sometimes on the Medina; at one point a 
little Niagara limestone seems to come in above the Crab 
Orchard shale. In Marion county the Corniferous rests directly 
upon the Crab Orchard shales. In Garrard county the Cornif- 
erous frequently rests directly upon the Crab Orchard shale, but 
sometimes the limestone layer with rounded quartz grains, already 
mentioned, possibly Oriskany, intervenes. In Clark county the 
Oriskany is well recognized, and rests on the Niagara shale. All 
this is in keeping with the other facts already mentioned, in accord- 
ance with which the sandy, detrital elements increase in the Lower 
Silurian, in the Cumberland sandstone, in the Medina, the Crab 
Orchard shales, and various later rocks, on going southward. 
As already stated, the heavy beds of the Niagara are absent 
in the southern and eastern counties of Kentucky. Going north- 
eastward the Oriskany disappears near the middle of Bath, and 
the Corniferous in Fleming county. They do not appear again 
until Highland county, Ohio, is reached. 
