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Alluvium (Qa)
Topography
The alluvium forms valley flats, floodplains, and, in the Kentucky River
Valley, terraces. Flats are dissected by short, steep-sided gullies
near tributaries.
Hydrology
The alluvium yields small to large quantities of water to drilled wells,
depending on 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. The alluvium is too thin and fine-grained elsewhere to
yield large amounts of water. Water is hard.
Grant Lake Limestone/Fairview Formation (Oaf)
Topography
These formations create gently to moderately rolling uplands away from
major streams, with moderately dissected uplands where shale content
increases. They create steep, dissected slopes along large streams.
Ledges of thick limestone beds in these formations occur on steep hillsides
and bluffs along streams. Streams in uplands produce broad, flat valleys
where thick limestone beds are present, and may have small sinkholes
with minor underground drainage. Low hills on uplands also may be capped
by thick limestone beds. The lower part forms broad, flat ridges between
steep-sided valleys cut into the underlying shale of the Kope Formation.
Hydrology
These formations yield 100 to 500 gallons per day to drilled wells in
valley bottoms and along streams on uplands. They yield more than 500
gallons per day from thick limestone beds in broad valley bottoms, but
almost no water to wells on hillsides or hilltops. They may yield some
water to dug wells on ridgetops, and water to small springs. Small perennial
springs occur in the lower Grant Lake Limestone. Water is hard, and
in valley bottoms may contain salt or hydrogen sulfide. The relatively
impermeable shale prevents circulation of large quantities of groundwater
in joints and bedding-plane openings of relatively soluble underlying
limestone. As a result, the limestone beds have few solutionally enlarged
openings, and little water is available to wells and springs. However,
near the base of the Grant Lake, there is 25 feet or more of limestone
with small amounts of shale (Bellevue Limestone Member). Where this
limestone occurs at and below stream level in valley bottoms or along
streams on the uplands, fractures and bedding-plane openings have been
enlarged by solution; many small springs flow from outcrops, and some
drilled wells along streams yield more than 500 gallons per day.
Kope and Clays Ferry Formations (Okc)
Topography
These formations lie in broad, flat valley bottoms along large streams
between steep, narrow ridges. Limestone has undergone solution, and
in some areas is characterized by small sinkholes and subsurface drainage.
Smaller streams develop long, narrow, winding, V-shaped valleys.
Hydrology
These formations yield more than 500 gallons per day to wells drilled
in valley bottoms and small amounts of water to wells on hillsides and
hilltops. They yield water to small springs. Water is hard or very hard
and may contain salt or hydrogen sulfide, particularly in wells in valley
bottoms; both undesirable constituents, 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. Some wide, flat
areas have small sinkholes and some underground drainage.
Lexington Limestone (Tanglewood Limestone, Grier, Logana Members)
(Ol)
Topography
The Lexington lies in flat valley bottoms along the Kentucky River.
Hydrology
The Lexington yields more than 500 gallons per day to wells, and as much as
150 gallons per minute in places. Water is hard and may contain salt or hydrogen
sulfide in some places.
High Bridge Group (Ohb)
Topography
The High Bridge has no surface exposure in this quadrangle, but underlies
the entire area.
Hydrology
The High Bridge is not likely to yield usable amounts for any use. It
is not considered an aquifer in this area.
Knox Group (Okx)
Topography
The Knox has no surface exposure in Kentucky, but underlies the entire
state at varying depths.
Hydrology
In central 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 from 10 to
20 gallons per minute, 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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