Alluvium (Qa) / Glacial Deposits (Qg)
These deposits form valley flats, terraces, and floodplains in the rather
narrow Ohio River Valley where terraces are long, narrow, and discontinuous.
The alluvium is thin in tributary streams, but may form floodplains
and small terraces along broad valleys.
These deposits yield moderate to large quantities of water to drilled
wells in the Ohio River Valley according to thickness and texture; they
commonly yield 200 gallons per minute, and as much as 800 gallons per
minute from gravel-packed wells. The alluvium is too thin and fine grained
in tributary valleys to yield large quantities of water. Water is hard
and may contain salt or hydrogen sulfide.
Crab Orchard Formation (Scb)
Shale forms steep, dissected hillsides and flat valley bottoms and upland
The Crab Orchard yields 100 to 500 gallons per day to wells in valley
bottoms or along major streams on uplands, but almost no water to wells
on hills. It does yield water to small springs and seeps. Water is hard
and locally contains large amounts of magnesium and calcium sulfate
dissolved from epsom salt and selenite (gypsum) in the shale.
Brassfield Dolomite (Scb)
The Brassfield forms discontinuous ledges along hillsides.
The Brassfield yields almost no water to wells. Dolomite beds yield
moderately hard to hard water to small springs.
Drakes Formation (Od) / Bull Fork Formation (Ob)
These formations provide gently to moderately rolling uplands. Along
large streams there is considerable dissection, with slopes moderately
steep where underlain by shale, and moderately undulating to gently
rolling where underlain by limestone. Steep and cliffy slopes are littered
with limestone slabs left as shale beds weather and wash away.
These formations yield 100 to more than 500 gallons per day to drilled
wells in broad valleys and along streams in uplands, but almost no water
to drilled wells on hillsides or ridgetops. They do yield water to small
springs. Water is hard, and in valley bottoms may contain salt or hydrogen
sulfide. Shale limits the amount of water that has access to thick limestone
beds, and therefore restricts the number of openings in these beds enlarged
by solution. As a result, the limestone beds yield little water. In
locations where groundwater has ready access to thick limestone beds
along streams, wells and springs have larger yields.
Grant Lake Limestone / Fairview Formation (Oaf)
These formations create gently to moderately rolling uplands, except
along major streams, where there is considerable dissection that leaves
steep slopes. Thick limestone beds stand out as ledges on steep hillsides
and bluffs along streams; where present on uplands, they underlie broad,
flat valleys that may have small sinkholes and some underground drainage.
These formations yield 100 to 500 gallons per day to drilled wells in
broad valleys and along streams in uplands, but almost no water to drilled
wells on hillsides or ridgetops. They yield 100 to 500 gallons per day
to wells drilled into thick limestone beds along streams in uplands.
Thick limestone beds yield water to small springs along valley bottoms
and hillsides. Water is hard, and in valley bottoms may contain salt
or hydrogen sulfide.
Kope Formation (Ok)
TheKope forms rugged, much dissected topography of long, narrow, steep-sided
ridges and narrow, winding, V-shaped valleys with dendritic drainage
pattern. Steep slopes are littered with thin limestone slabs that remain
as shale erodes and washes away. The contrast with less rugged upland
surfaces of adjacent areas is marked, except near major streams, where
change is masked by dissection.
The Kope yields 100 to 500 gallons per day to drilled wells in valley
bottoms along large streams, but almost no water to drilled wells on
hillsides or ridgetops. It does yield water to small springs and seeps.
Water is hard in valley bottoms, and may contain salt or hydrogen sulfide.
Shale units have small, poorly connected openings that allow passage
of only small quantities of water, restricting yields to wells and springs
and preventing recharge to underlying rocks.
Clays Ferry Formation and Its Point Pleasant Tongue (Okc)
These rocks form broad valleys along large streams between steep, narrow
ridges. Limestone has undergone solution and in some areas is characterized
by small sinkholes and subsurface drainage.
The Clays Ferry yields more than 300 gallons per day to wells drilled
in valley bottoms and small amounts of water to wells on hillsides and
hilltops. It also yields water to small springs. Water is hard or very
hard, and may contain salt or hydrogen sulfide, particularly in wells
in valley bottoms; both, especially hydrogen sulfide, may be found in
wells on hillsides. Beneath broad interstream areas, much solutional
enlargement of fractures and bedding-plane openings has taken place
in the soluble zones beneath tributary streams, and many drilled wells
produce 100 to 500 gallons per day.
The U.S. Geological Survey's Hydrologic Atlas Series, published cooperatively
with the Kentucky Geological Survey, provides hydrologic information
for the entire state. Atlases for the county are HA-16,
to "Groundwater Resources in Kentucky"