The alluvium forms broad terraces along the relatively wide Licking
River Valley. It is too thin in tributary valleys to have distinctive
The alluvium yields small to large quantities of water to drilled wells,
depending on texture and thickness of material. It yields more than
500 gallons per day in the Licking River valley, and as much as 150 gallons per minute
in places. Elsewhere it is too thin and fine-grained to yield enough
water. Water is hard.
High-Level Fluvial Deposits (QTf)
These deposits lie on the tops of low hills near Licking and North Fork
In most areas away from the Ohio River, these deposits are generally
too thin and scattered to be
important as an aquifer, yielding small amounts of water to wells and
Ashlock Formation, Calloway Creek Limestone (Oaf)
These formations underlie gently to moderately rolling uplands away
from major streams, more
highly dissected where shale content increases. Small sinkholes, minor
and broad, flat valleys occur where limestone predominates.
These formations yields 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 do yield water to
small springs. Water is hard and in valley bottoms may contain salt
or hydrogen sulfide. Where
thick limestone beds with little shale occur below stream level in valley
bottoms or on uplands,
they may have undergone solutional enlargement of fractures and bedding-plane
Wells drilled into these limestone beds may produce more than 500 gallons per day.
These thick beds
also yield water to some large springs.
Garrard Siltstone (Okc)
The Garrard forms prominent ledges along hillsides.
The Garrard yields 100 to 500 gallons per day to drilled wells in valley
bottoms, but almost no water to wells on hillsides or ridgetops, and
little water to springs. The well-cemented siltstone and fine-grained
sandstone and siltstone do not provide many openings for water, and
yield almost no water to wells. Water is hard.
Clays Ferry and Kope Formation (Okc)
These formations provide rugged topography of narrow, steep-sided ridges
with narrow V-shaped valleys of dendritic drainage. Shales on steep
slopes erode easily and are covered with thin limestone slabs in many
places. In the lower part of the formation, topography becomes more
gently to moderately rolling uplands, with small sinkholes and some
underground drainage where limestone predominates.
The Clays Ferry and Kope yield 100 to 500 gallons per day to drilled
wells in large valley bottoms along streams, but almost no water to
drilled wells on hillsides or ridgetops. They do yield water to small
springs and seeps. Water is hard in valley bottoms and may contain salt
or hydrogen sulfide. Shale has small, poorly connected openings, and
ground-water circulation is slow; as a result, little water is available
to wells and springs. On ridgetops the shale prevents downward percolation
of water, and creates small semiperched water bodies in the lower part
of the soil and the upper part of weathered bedrock.
Upper Part of Lexington Limestone (Ol) (Stodes Creek, Millersburg,
Tanglewood Limestone, Devils Hollow, Stamping Grounds, Sulpher Well,
The upper Lexington forms gently sloping hillsides adjacent to small
streams in uplands. The resistant shale and soft bentonite-rich beds
form a subdued bench-like topography along hillsides and streams.
The upper Lexington yields 100 to 500 gallons per day to wells in valley
bottoms and along streams in uplands. It yields as much as 300 gallons
per minute in some places where thick limestone beds occur at or below
stream level along large streams. It also yields water to springs in
the Tanglewood Limestone and Brannon Member. Generally, the upper part
of the Lexington Limestone contains more shale and yields less water
compared to the lower part, which is mostly limestone in many places.
Water is hard and may contain salt or hydrogen sulfide in some places.
Water from wells near fault zones may contain objectionable amounts
Knox Group (Okx)
The Knox has no surface exposure in Kentucky, but underlies the entire
state at varying depths.
In the Inner Bluegrass Region of Kentucky, fresh water has been found
in the upper 100 to 250 feet of this largely untested dolomite-rich
aquifer. Wells often exceed 750 feet in total depth, with high concentrations
of dissolved solids found in many areas. Average reported yields range
in the 10 to 20 gallons per minute range, but as high as 75 gallons
You can find out more about the Knox
The U.S. Geological Survey's Hydrologic
Atlas Series, published cooperatively with the Kentucky Geological
Survey, provides hydrologic information for the entire state.
to "Groundwater Resources in Kentucky"