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Alluvium (Qa)
Topography
The alluvium forms extensive floodplains with small terraces along Rolling
Fork, and narrow floodplains and small terraces along Beech Fork and
larger tributaries.
Hydrology
The alluvium yields 100 to more than 500 gallons per day from thick
deposits along Rolling Fork. It is too thin and fine grained to yield
much water along Beech Fork and the large tributaries. Water is hard
and may have a high iron content.
Ste. Genevieve (Mgl)
Topography
The Ste. Genevieve underlies rolling karst areas.
Hydrology
The Ste. Genevieve yields more than 50 gallons per minute to wells from
large solution openings in karst areas. Most wells encounter 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 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 Limestone (Mgl)
Topography
The St. Louis underlies rolling karst areas. It commonly has less relief
than karst on the Ste. Genevieve Limestone, but sinkholes are steeper.
Hydrology
The St. Louis yields more than 50 gallons per minute to wells from large
solution openings in karst areas. Most wells penetrate solution openings,
but may be inadequate for a domestic supply with a power pump. The St.
Louis has a major spring horizon; many springs have low flows of several
hundred to several thousand gallons per minute. Many springs are used
for public and industrial water supplies.
Salem, Harrodsburg Limestones (Msh)
Topography
These limestones underlie gently rolling uplands, the tops of some knobs,
and the Mississippian Escarpment (Muldraugh Hill) in southern Marion
County. They form steep bluffs above exposures of the Borden Formation.
Hydrology
These limestones yield 100 to 500 gallons per day to drilled wells on
broad ridges or on upland. They may yield larger amounts when solution
openings are encountered close to perennial stream level. They yield
water to springs at the heads of ravines and on the face of escarpments.
Wells that encounter large solution openings produce more than 5 gallons
per minute. Water from wells is hard, but otherwise of good quality.
Borden Formation (Muldraugh [Mbf], Halls Gap, Nancy, New Providence
Members) (MDbb)
Topography
The Borden is the main part of the Muldraugh Escarpment, ridges, and
knobs. Resistant rocks of the Muldraugh Member cap the escarpment and
larger knobs. Minor limestone beds form ledges and small cliffs. The
New Providence Member underlies the lower, dissected slopes of the knobs
and escarpment and forms broad flat valleys in southern Marion County.
Shale forms steep slopes, and the more resistant siltstone beds form
ledges on slopes and in ravines.
Hydrology
The Borden yields 100 to 500 gallons per day to wells in valley bottoms,
and may yield more than 500 gallons per day where thick siltstone beds
occur at and below stream level. It yields almost no water to wells
on hills, but does yield water to small springs in the limestone and
siltstone beds. Water from the shale is soft; from the siltstone, hard;
and from the limestone, very hard. At shallow depths below stream level,
water may contain salt, sulfate, or iron. The silty shale and siltstone
are favorable for dug wells, which are common in this area. Most dug
wells yield less than 500 gallons per day and many yield little or go
dry in late summer and early fall. The New Providence Shale Member yields
little or no water to wells.
New Albany Shale (MDnb)
Topography
The shale forms broad, flat valleys with steep hillsides, and steep,
dissected bluffs along streams.
Hydrology
The shale yields 100 to 500 gallons per day to drilled wells in broad
valleys and on uplands. It yields water to dug wells almost any place
in the black shale, although such wells are susceptible to surface pollution.
The New Albany yields water to small springs, which often go dry during
late summer and fall. Water is in fractures that extend less than 50
feet below land surface. Water is hard and may contain salt or hydrogen
sulfide.
Laurel Dolomite (Slb)
Topography
The Laurel Dolomite forms tops of ridges, ledges on steep hillsides,
and lies in bluffs along streams.
Hydrology
The Laurel yields 100 to 500 gallons per day to drilled wells in valley
bottoms, on broad ridges, and along streams on uplands. It yields water
to many springs. Water is hard.
Osgood Formation (Slb)
Topography
The Osgood forms steep, dissected hillsides. It erodes easily, undermining
the Laurel.
Hydrology
The Osgood yields almost no water, impedes recharge to the Drakes Formation,
and holds up water in the Laurel. Limestone yields water to small springs.
Water is hard.
Brassfield Formation (Slb)
Topography
The Brassfield forms ledges on slopes and tops of small cliffs.
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,
Odc) and Bull Fork Formation (Ob)
Topography
These formations create somewhat dissected upland areas, with moderately
steep slopes where shale predominates, and moderately undulating to
gently rolling surfaces where limestone predominates. Slopes are steep
to cliffy and dissected along large streams; many are littered with
limestone slabs left after shale erodes and washes away. Small sinkholes
with some underground drainage are present where thick limestone beds
occur along broad upland stream valleys.
Hydrology
The Drakes and Bull Fork yield 100 to 500 gallons per day to drilled
wells in broad valleys and along streams on 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. Shale prevents circulation of water in thicker limestone beds,
except where limestone is exposed on flat ridges or valley bottoms.
Grant Lake Limestone, Calloway Creek Limestone (Oaf)
Topography
These formations create gently to moderately rolling uplands away from
major streams. They are more highly dissected where shale content increases.
They are dissected and steep along large streams. Thick limestone beds
stand out as ledges along steep hillsides and bluffs along streams,
and where present on uplands they underlie broad, flat valleys that
may have small sinkholes and some underground drainage. The lower part
of the Calloway Creek caps broad, flat ridges between steep-sided valleys
cut into underlying shale of the Clays Ferry Formation.
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,
but almost no water to drilled wells on hillsides or ridgetops. They
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. A 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)
Topography
The Clays Ferry forms the rugged, dissected topography of long, narrow,
winding, steep-sided ridges with narrow, winding, V-shaped valleys of
the dendritic drainage pattern. Shales on steep slopes erode easily
and are covered with thin limestone slabs in many places. The contrast
with the rolling upland outcrop areas of the overlying Drakes, Grant
Lake, and Calloway Creek Formations is striking, except along large
streams, where change is masked by dissection.
Hydrology
The Clays Ferry yields 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. It may yield some water to dug wells on ridgetops.
It does yield water to small springs and seeps. Water is hard, and in
valley bottoms may contain salt or hydrogen sulfide. Shale has small,
poorly connected openings, and groundwater circulation is slow. On ridgetops,
the shale impedes downward percolation of water and holds up water in
the soil and weathered-rock zone. Dug wells, having large wall areas,
are best suited for obtaining this water, but are susceptible to pollution
by surface sources. On broad ridges capped by the Grant Lake or Calloway
Creek Formations, the underlying Clays Ferry holds up a semiperched
water body in the Grant Lake and Calloway Creek, and dug wells produce
some water; however, wells often go dry in late summer and fall.
Lexington Limestone (Ol)
Topography
The Lexington has no surface exposure in the county, but underlies the
entire area.
Hydrology
The Lexington yields more than 500 gallons per day to wells in valley
bottoms and 100 to 500 gallons per day to wells in small valleys. 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 the 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
There is no surface exposure of the Knox in Kentucky, but it 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 can be as high as 75 gallons per minute.
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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