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Alluvium (Qa)
Topography
The alluvium underlies floodplains and terraces of the Cumberland and
Tennessee Rivers and tributaries.
Hydrology
The alluvium of the Cumberland River may yield several hundred gallons
a minute to drilled wells. The alluvium yields enough water for a modern
domestic supply (more than 500 gallons per day) to nearly all wells.
The alluvium yields practically no water to wells in small valleys,
where it is thin and fine grained.
Terrace gravel deposits and continental deposits (Qtc)
Topography
These deposits occur on uplands and eroded edges of uplands above 370
feet.
Hydrology
These deposits yield small quantities of water suitable for household
use. One spring had a measured discharge of 47 gallons per minute. Most
wells yield less than 10 gallons per minute. Water-bearing gravel usually
overlies clay or indurated layers. Water ranges in hardness from 8 to
724 parts per million and in dissolved solids from 43 to 782 parts per
million. Iron content is generally low.
Tuscaloosa Formation (Kt)
Topography
The Tuscaloosa may occur in remnants of a channel eroded into the surface
of the Paleozoic rocks. It underlies dissected ridges adjacent to Kentucky
Lake.
Hydrology
The Tuscaloosa is not significant as an aquifer. Most drilled wells
in the gravel of the formation are adequate for a bailer (more than
100 gallons per day). Yields are low, because of the clayey matrix and
poor sorting. Tripolitic clay is present locally; it tends to clog well
screens, and wells penetrating it are inadequate (less than 100 gallons
per day). Hardness of water from two wells sampled was 26 and 57 parts
per million, and dissolved solids content was 50 and 76 parts per million.
Yields adjacent to Kentucky Lake may exceed 5 gallons per minute.
Clayton and McNairy Formations (TKcm)
Topography
Badlands are formed where McNairy sand crops out in southern Trigg County.
Hydrology
These formations yield sufficient water for domestic use near the outcrop
area of Paleozoic bedrock and in areas of perched water. Where the formation
is thick, drilled wells yield as much as 830 gallons per minute. In
areas where the formation is mostly silt and clay, there may not be
sufficient saturated sand to furnish even a domestic supply. Hardness
of water ranges from 13 to 182 parts per million, and dissolved solids
from 62 to 275 parts per million. Iron may be present in objectionable
amounts.
Chesterian formations (Glen Dean Limestone, Golconda Formation,
Cypress Sandstone, Paint Creek Shale, Bethel Sandstone) (Mcl)
Hydrology
In the northern two-thirds of Trigg County, these formations yield small
amounts to wells and springs in outcrop areas. Water from Mississippian
rocks underlying younger rocks contains salt in objectionable, amounts,
if any water is found.
In the southwestern part of the county, most drilled wells that obtain
water from fault zones are adequate for a domestic supply. Yields are
as much as 100 gallons per minute. Flows of as much as 20 gallons per
minute are obtained from fractures along fault zones and adjacent beds.
Most flowing wells are in sandstone. Water is usually obtained from
the hanging walls or gouge zones of faults. Most shallow wells in broad
uplands are dug and usually yield more than 100 gallons per day, but
yields are not dependable in dry years. Most drilled wells produce enough
water for residential use. Minor spring horizons occur near the base
of the sandstone on discontinuous shale beds. Very few of the springs
are adequate for a domestic supply, and many go dry in late fall or
winter.
Limestone formations yield small to adequate supplies from solution
openings. In lowland areas bordering streams, some wells furnish enough
for a domestic supply. Most wells in upland areas are inadequate for
a domestic supply. On uplands, deep wells that penetrate solution openings
in limestone may produce more than 5 gallons per minute, but most deep
wells on uplands are inadequate for a domestic supply. Close to outcrop
areas, particularly near major escarpments, yields from perched water
bodies generally are inadequate during dry periods. Springs occur at
the base of many limestone formations, where they crop out on escarpments
and hillsides. Adjacent to large upland areas, springs yield as much
as 100 gallons per minute and low flows are more than 5 gallons per
minute from some springs.
Glen Dean Limestone (Mcl)
Topography
The Glen Dean underlies gently rolling uplands. It forms a gradual
slope above the Hardinsburg bench.
Hardinsburg Sandstone (Mcl)
Topography
The Hardinsburg forms a minor escarpment, modified in many places
by faults. It also underlies broad rolling uplands.
Golconda Formation (Haney Limestone, Big Clifty Sandstone, Beech
Creek Limestone Members) (Mcl)
Topography
The Golconda underlies gently rolling uplands and forms a steep slope
below the minor Hardinsburg Sandstone escarpment.
Cypress Sandstone (Mcl)
Topography
The Cypress forms a major escarpment. It underlies broad flat uplands.
Paint Creek Limestone (Mcl)
Topography
The Paint Creek forms moderate to rolling slope below the Cypress
Sandstone escarpment.
Bethel Sandstone (Mcl)
Topography
The Bethel forms the lowest major escarpment in the northern part
of the county. It also underlies broad rolling uplands.
Renault Limestone (Mcl)
Topography
The Renault forms a moderate slope under the Bethel Sandstone escarpment,
except where modified by faults or a higher sandstone escarpment.
Hydrology
The Renault yields little or no water to wells. Small springs with low
flows of about 5 gallons per minute occur near the top of the formation.
Ste. Genevieve Limestone (Mgl)
Topography
The Ste. Genevieve underlies rolling karst uplands. It forms moderate
slopes under the Bethel Sandstone escarpment, except where modified
by faults.
Hydrology
The Ste. Genevieve yields more than 50 gallons per minute to wells from
large solution openings in karst areas. Most wells penetrate solution
openings, but in areas high above perennial streams these solution openings
are dry in late summer and fall, and many wells are inadequate. Springs
having low flows ranging from less than 10 gallons per minute to about
1,500 gallons per minute occur at or near stream level. Smaller springs
discharge from perched water bodies in upland areas, but many go dry
during late summer and fall.
St. Louis and Salem Limestone (Mgl)
Topography
These limestones underlie dissected uplands and ridges. They also underlie
the rolling karst uplands of Trigg County. They form steep valley walls
along the Cumberland River.
Hydrology
Low flows of numerous springs that discharge from near the top of the
formation and near stream level range from less than 10 gallons per
minute to about 1,500 gallons per minute. Maximum flows range from less
than 100 gallons per minute to more than 100,000 gallons per minute.
Most springs are situated near minor rivers. In karst areas, drilled
wells generally produce enough water for domestic use. Some produce
more than 50 gallons per minute from large solution openings. Most wells
high above perennial streams are adequate. In nonkarst areas, yields
generally are lower than in karst areas; the number of solution openings
is fewer and their size smaller. Many wells are insufficient for domestic
use. Most springs are small, and many go dry during late summer and
fall. Most wells high above perennial streams are inadequate.
Warsaw Limestone (Mw)
Topography
The Warsaw underlies dissected uplands and ridges adjacent to the Cumberland
River and tributaries in Trigg County.
Hydrology
Wells that encounter large solution openings near stream level or near
sinkholes yield sufficient water for a power pump. In most other areas,
the rock is fine grained and yields generally are insufficient for a
bailer or bucket (less than 100 gallons per day).
Fort Payne Formation (Mbf)
Topography
The Fort Payne underlies dissected ridges between the Tennessee and
Cumberland Rivers.
Hydrology
The Fort Payne yields almost no water to wells where unweathered. Where
the limestone has been leached away and chert rubble is left, yields
may exceed 50 gallons per minute. Yields of most wells of moderate depth
range from 2 to 10 gallons per minute. Tripolitic clay may be present
in some areas where the formation yields little or no water to wells.
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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