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Alluvium (Qa) and glacial sediments (Qg)
Topography
These sediments form floodplains and terraces, as much as 6 miles wide,
in the Ohio River Valley. Some Ohio River terraces are as much as 80
feet above normal pool stage. Flats are dissected by short, steep-sided
gullies near tributaries.
Hydrology
These sediments yield 200 to 500 gallons per minute to most wells that
penetrate the full thickness of alluvium in the Ohio Valley, and more
than 1,000 gallons per minute to large-diameter wells. They yield 100
to 500 gallons per day to wells in tributary-stream valleys, and may
yield more than 500 gallons per day where gravel is present. Water is
hard, and the iron content may be high near the Ohio River Valley walls.
Louisville Limestone (Slw)
Topography
The Louisville Limestone forms broad ridges in western Trimble County,
and cliffs and ledges in valley sides.
Hydrology
The Louisville yields more than 500 gallons per day to wells drilled
in valley bottoms or along streams on broad uplands, and as much as
50 gallons per minute in places. It yields water to springs at the contact
with the underlying Waldron Shale. Water is hard and may contain salt
or hydrogen sulfide below stream level.
Waldron Shale (Slw)
Topography
The Waldron forms slopes between limestone ledges on hillsides; erosion
of shale undermines the overlying Louisville Limestone.
Hydrology
The Waldron yields almost no water to wells or springs. It holds up
water in the overlying Louisville Limestone and prevents recharge to
the underlying Laurel Dolomite.
Laurel Dolomite (Slb)
Topography
The Laurel forms ledges and cliffs along streams.
Hydrology
The Laurel yields 100 to 500 gallons per day to wells on broad ridges
and along streams. It yields water to small springs at contact with
the underlying Osgood Formation. Water is hard.
Osgood Formation (Slb)
Topography
The Osgood forms slopes between ledges above and below.
Hydrology
The Osgood yields almost no water from shale. It does yield water from
limestone to seeps. It impedes recharge to underlying rocks. Water is
hard.
Brassfield Formation (Slb)
Topography
The Brassfield forms ledges on slopes and tops of small cliffs of the
underlying Saluda Limestone.
Hydrology
The Brassfield yields almost no water to wells, but does yield water
to seeps and small springs.
Water is hard.
Drakes Formation (Saluda Dolomite, Bardstown, Rowland Members) (Od)
and Bull Fork
Formation (Ob)
Topography
The Drakes and Bull Fork underlie moderately dissected upland areas,
forming moderately steep slopes where shale predominates and less steep
slopes where limestone predominates. Steep slopes occur along large
streams and cliffs; many slopes are dotted with weathered limestone
slabs. Solutional features are evident where thick limestone beds underlie
streams.
Hydrology
These formations yield 100 to 500 gallons per day to wells in large
stream valleys, and more where thick limestone is present. They yield
almost no water to wells on hillsides and ridges, except in broad ridges
in the upper part of the formation. They do yield water to small springs.
Water is hard and may contain salt in valley bottoms, but generally
is of good quality.
Grant Lake Limestone, Fairview Formation, Calloway Creek Limestone (Oaf)
Topography
These formations underlie gently to moderately rolling uplands away
from major streams. They are more highly dissected where shale content
increases, with small sinkholes, minor underground drainage, and broad,
flat valleys where limestone predominates. The lower part forms broad,
flat ridges between steep-sided valleys cut into underlying shale of
the Kope or Clays Ferry Formations.
Hydrology
These formations yield 100 to 500 gallons per day to drilled wells in
broad valleys and along streams in uplands. They yield more than 500
gallons per day from thick limestone beds in the broad valley bottoms.
They yield almost no water to drilled wells on hillsides or ridgetops,
but do yield water to small springs and seeps. Limestone beds 15 feet
thick in the lower part of the Grant Lake Limestone yield as much as
30 gallons per minute to springs. The sandy zone near the base yields
little water. Water is hard, and in valley bottoms may contain salt
or hydrogen sulfide.
Clays Ferry Formation (Okc) and Kope Formation (Ok)
Topography
These formations create a 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. The contrast with the less rugged surface of the adjacent areas
is marked, except near major streams. 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 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 yield water to small springs and seeps.
Water is hard in valley bottoms, and may contain salt or hydrogen sulfide.
Lexington Limestone (Ol)
Topography
The Lexington has no surface exposure in Trimble County, but underlies
the entire area.
Hydrology
The Lexington is not likely to yield usable amounts for any use. It
is not considered an aquifer in
this area.
High Bridge Group (Ohb)
Topography
The High Bridge has no surface exposure in Trimble County, 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, and high concentrations of dissolved
solids are found 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. It is not likely to yield usable amounts for any use in Trimble
County. It is not considered an aquifer in this area.
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. Atlases
covering the county are: HA-23,
HA-97.
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