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. It
yields little water to springs. The well-cemented siltstone and fine-grained
sandstone and siltstone do not provide many openings for water, and
yields almost no water to wells. Water is hard.
Clays Ferry Formation (Okc)
The Clays Ferry forms 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 yields 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 ridge tops. It yields 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 groundwater 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) (Strodes Creek, Millersburg,
Tanglewood Limestone, Devils Hollow, Stamping Ground, Sulfur Well, Brannon
The upper Lexington forms broad flat valleys in uplands, with well-developed
subsurface drainage and many sinkholes. It 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 or more to wells
in valley bottoms and along streams in uplands, and as much as 300 gallons
per minute in some places where thick limestone beds occur at or below
stream level along large streams. Springs occur in the Tanglewood Limestone
and Brannon Member. Yields to many perennial springs are 100 to 500
gallons per day and more than 100 gallons per minute to a few large
springs. The amount of water available in rocks of the Lexington Limestone
is dependent on the amount of shale. Generally, the upper part of the
Lexington Limestone contains more shale and yields less water in contrast
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 of salt.
Lower Part of Lexington Limestone (Ol) (Grier, Logana, Curdsville
The lower Lexington forms rolling to dissected uplands. Sinkholes are
very common, the large ones occurring in the Grier Limestone. Underground
drainage is well developed. Natural outcrops are rare in the rolling
upland, but the resistant limestone beneath hillslopes is evident from
the subdued bench-like or terrace-like appearance of the slopes. Limestone
crops out in discontinuous bands in the valley sides in the dissected
part near the Kentucky River.
The lower Lexington yields more than 500 gallons per day to wells in
valley bottoms and along streams in uplands. It yields up to 150 gallons
per minute from thick limestone beds in the Curdsville along large streams,
and yields water to many small and large springs. The amount of water
available in rocks of the Lexington Limestone is dependent on the amount
of shale. Generally, the upper part of the Lexington Limestone contains
more shale and yields less water in contrast 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 of salt.
High Bridge Group (Tyrone Limestone, Oregon Formation, Camp Nelson
The High Bridge forms steep slopes and high cliffs along the Kentucky
and Dix Rivers and lower parts of tributaries. The Camp Nelson forms
flat terraces with occasional sinkholes in the bottom of the Kentucky
River gorge and steep cliffs along the lower sides. It also extends
up the large tributaries, forming flat bottoms and steep walls. The
Oregon crops out in a band in the walls of the gorge and up a few large
tributaries. The Tyrone crops out in the upper walls of the Kentucky
River Gorge and extends up the large tributaries nearly to the upland,
forming broad, flat valleys with sinkholes and underground drainage.
The High Bridge Group yields 100 to more than 500 gallons per day to
drilled wells in valleys of the Dix and Kentucky Rivers and large tributaries,
and yields as much as 30 gallons per minute to drilled wells along the
shores of Herrington Lake. Yields have been reported as much as 225
gallons per minute to wells drilled into the Camp Nelson Limestone adjacent
to the Kentucky River, from solution channels and fractures connected
with the river. The limestones yield water to springs on hillsides and
in steep walls along large streams. Water is hard and may contain hydrogen
sulfide, but is generally of good quality. Wells drilled into the High
Bridge through overlying rocks produce almost no water because bentonite
beds in the Tyrone prevent recharge to underlying rocks, except where
the bentonite has been breached or removed by erosion.
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 and have high concentrations
of dissolved solids in many areas. Average reported yields range from
10 to 20 gallons per minute, but are as high as 75 gallons per minute.
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"