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Alluvium (Qa)
Topography
The alluvium forms narrow floodplains and small terraces along the larger
streams.
Hydrology
The alluvium is generally inadequate for a domestic supply, being too
thin and fine-grained to yield much water. Water is hard.
St. Louis Limestone (Mgl)
Topography
The St. Louis underlies rolling karst areas in uplands and tops of flat-topped
ridges in southern Lincoln County. Thick limestone beds form ledges
and cliffs. Resistant siltstone and nonresistant shale layers form discontinuous
minor benches on hillsides.
Hydrology
The St. Louis yields more than 50 gallons per minute to wells from large
openings in karst areas. Most wells penetrate some solution openings,
but where openings are small, yields are inadequate for a domestic supply.
A major spring horizon occurs near the top of the formation in the karst
areas. Many seepage springs occur throughout the formation; low flows
range from less than 10 gallons per minute to more than 500 gallons
per minute. The lower part of the formation is composed of siltstone
and argillaceous limestone. Yields from these sedimentary rocks are
low and generally not adequate for a domestic supply with bailer or
bucket.
Salem and Warsaw Formations (Msh)
Topography
These formations underlie moderately to highly dissected rolling uplands.
In some areas, numerous small sinkholes occur in the Warsaw.
Hydrology
These formations yield enough water for a domestic supply where dominantly
limestone. Yields are low where siltstone or argillaceous limestone
is penetrated. A minor spring horizon occurs at the contact of the limestone
with the underlying siltstone or argillaceous limestone. Another spring
horizon occurs near the contact of the Warsaw and Fort Payne. Low flows
generally are less than 5 gallons per minute.
Borden Formation (MDbb), (Mbf)
Topography
The Borden forms the main part of the Mississippian escarpment, ridges,
and knobs. Shale forms
dissected slopes, massive siltstone forms cliffs, and limestone forms
ledges on shale slopes.
Hydrology
The Bordent yields 100 to 500 gallons per day to wells in valley bottoms, and
may yield more than 500 gallons per day to drilled wells in broad valley bottoms
from fractured sandy rocks near streams. It yields almost no water to
wells on hills. Water from wells drilled below stream level may contain
salt, sulfate or iron less than 100 feet below the level of the principal
valley bottoms. Water from dug wells and small springs is soft and has
a low dissolved-solids content. Water from shale is soft, from the siltstone,
hard, and from the limestone, very hard. Because much of this formation
is soft and silty, it has been well suited to the construction of dug
wells in the past.
New Albany Shale (MDnb)
Topography
The New Albany forms broad, flat valleys and flat upland surfaces; steep,
dissected hillsides and bluffs along streams.
Hydrology
The New Albany yields 100 to 500 gallons per day to drilled wells in valley
bottoms and on uplands usually at depths of less than 50 feet; water
from greater depths is highly mineralized. Yields water to small springs.
Water may be soft or highly mineralized. Salt, hydrogen sulfide, and
iron are the usual objectionable constituents.
Boyle Dolomite (MDnb)
Topography
Resistant ledges on valley sides between shale slopes above and below.
Hydrology
Yields almost no water to drilled wells; yields water to many small
perennial springs. Water is hard but otherwise of good quality.
Crab Orchard Formation and Brassfield Dolomite (Scb)
Topography
Shale forms steep, dissected hillsides and broad, flat valley bottoms;
erodes readily below more resistant overlying limestone, forming notches
and recesses. Dolomite beds form discontinuous ledges along hillsides.
Hydrology
Shale yields almost no water to wells or springs; may yield small amounts
of water to wells in valley bottoms. Water is highly mineralized. Dolomite
beds yield hard water to small springs.
Drakes Formation (Od)
Topography
The Drakes forms dissected upland areas, with slopes moderately steep
where underlain by shale, and moderately undulating to gently rolling
where underlain by limestone. Steep and cliffy slopes occur along large
streams, littered with limestone slabs left as shale beds weather and
wash away.
Hydrology
The Drakes yields 100 to 500 gallons per day to drilled wells in broad valleys
and along streams in upland, but almost no water to drilled wells on
hillsides or ridgetops. It does yield water to small springs. Water
is hard and in valley bottoms may contain salt or hydrogen sulfide.
Shale limits amount of water that has access to thick limestone beds,
and therefore restricts number of openings in these beds enlarged by
solution. As a result, the limestone beds yield little water.
Ashlock Formation and Calloway Creek Limestone (Oaf)
Topography
These formations create gently to moderately rolling uplands away from
major streams. The rocks are more highly-dissected where shale content
increases, and where limestone predominates with small sinkholes, minor
underground drainage, and broad, flat valleys.
Hydrology
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 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 openings. 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)
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 yields almost no water to
wells. Water is hard.
Clays Ferry Formation and Kope Formation (Okc)
Topography
These rocks form the 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
These formations yield 100 gallons per day to drilled wells in valley bottoms,
but almost no water to drilled wells on hillsides or ridgetops. The
do 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 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 lower part of soil and upper part
of weathered bedrock.
Upper Part of Lexington Limestone (Tanglewood Limestone, Millersburg,
Strodes Creek,
Devils Hollow, Sulfur Well, Brannon and Perryville Members) (Ol)
Topography
The upper Lexington forms broad flat valleys in uplands; where dominantly
limestone, the formations has well-developed subsurface drainage and
many sinkholes. It also forms gently sloping hillsides adjacent to small
streams in uplands. The resistant shale and soft bentonite-rich beds
form a subdued benchlike 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. Yields water to springs from 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 (Grier, Logana and Curdsville
Members) (Ol)
Topography
The lower Lexington forms rolling to dissected uplands. Sinkholes are
very common, the large ones occur in the Grier Limestone. Natural outcrops
are rare in the rolling upland, but the limestone beneath hill slopes
is evident from the benchlike 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, and 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 forms steep slopes and high cliffs along the Dix River
and lower parts of its tributaries.
Hydrology
The High Bridge yields 100 to more than 500 gallons per day to drilled
wells in valleys of the Dix River and large tributaries. It also yields
water to springs on hillsides and in steep walls along large streams.
Water is hard and may contain hydrogen sulfide, but generally is 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, with high concentrations
of dissolved solids found in many areas. Average reported yields range
in the 10 to 20 gallons per minute range but are 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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