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Alluvium (Qa)
Topography
The alluvium forms narrow floodplains and small terraces along the Kentucky
River, Elkhorn Creek, and larger tributaries.
Hydrology
The alluvium yields small to large quantities of water to drilled wells,
according to texture and thickness of material. It yields more than
20 gallons per minute from 60 feet of fine-grained material in the Kentucky
River Valley, and as much as 20 gallons per minute from 44 feet of similar
material in the valley of Elkhorn Creek. It is too thin and fine grained
elsewhere to yield large amounts of water. Water is hard.
High-level fluvial deposits (QTf)
Topography
These deposits blanket localized areas of uplands and hilltops having
no distinct surface
expression.
Hydrology
These deposits yield 100 to 500 gallons per day to wells in thick deposits,
but are too thin and scattered
to be important as an aquifer otherwise. The formation also yields water
to small springs and dug
wells. Water is soft.
Garrard Siltstone (Okc)
Topography
The Garrard forms prominent ledges along hillsides.
Hydrology
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)
Topography
This formation creates rugged topography of narrow, steep-sided ridges
with narrow V-shaped
valleys of dendritic drainage. 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.
Hydrology
This formation yields 100 gallons per day to drilled wells in valley
bottoms, but almost no water to drilled wells on hillsides or ridgetops.
It does yield water to small springs. In the lower, limestone-rich section,
drilled wells can yield 100 to 500 gallons per day in valley bottoms
along streams. 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 Grounds, Sulfur Well,
Brannon Members)
Topography
The upper Lexington underlies broad flat valleys in uplands. Where dominantly
limestone, it has a 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.
Hydrology
The upper Lexington yields more than 500 gallons per day to wells in valley
bottoms and along streams
in uplands. It yields 100 to 500 gallons per day to many perennial springs 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, throughout the whole Lexington
Limestone
section, the more shale found within the zone of interest, the less
water will be found. The
Lexington yields water to springs from the resistant Brannon Member.
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
Members)
Topography
The lower Lexington underlies rolling to dissected uplands. Sinkholes
are very common; the larger ones occur in the Grier Limestone. Natural
outcrops are rare in the rolling uplands, but the limestone beneath
hillslopes is evident from the 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.
Hydrology
The lower Lexington yields 100 to 500 gallons per day to wells in most 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. It also yields water to many small springs. Water is
hard and may contain salt in
valley bottoms.
High Bridge Group (Tyrone Limestone, Oregon Formation, Camp Nelson
Limestone) (Ohb)
Topography
The High Bridge Group lies in 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.
Hydrology
The High Bridge yields 100 to more than 500 gallons per day to drilled
wells in valley of the Kentucky River and large tributaries. Yields
as much as 225 gallons per minute have been reported to wells drilled
into the Camp Nelson Limestone adjacent to the Kentucky River, from
solution channels and fractures connected with the river. The High Bridge
yields 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)
Topography
The Knox has no surface exposure in Kentucky, but underlies the entire
state at varying depths.
Hydrology
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 in
the 10 to 20 gallons per minute range but can be as high as 75 gallons
per minute.
You can find out more about the Knox
aquifer.
The U.S. Geological Survey's Hydrologic
Atlas Series, published cooperatively with the Kentucky Geological
Survey, provides hydrologic information for the entire state.
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