The alluvium forms extensive floodplains with small terraces along
Rolling Fork, and narrow floodplains and small terraces along Beech
Fork and larger tributaries.
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.
Girkin Formation (Reelsville Limestone, Sample Sandstone, Beaver
Bend and Paoli Limestone) (Mcl), Bethel Sandstone of the Mooretown Formation
The Girkin forms the lower part of the Dripping Springs Escarpment and
underlies rolling karst areas. It contains numerous large sinks into
which the overlying sandstone has collapsed.
Most wells in upland areas are inadequate for domestic use; however,
some wells yield enough water for a domestic supply (more than 500 gallons
per day) from solution openings. Some wells produce more than 5 gallons
per minute from large solution openings. Near outcrop areas, particularly
near major escarpments, yields generally are inadequate during dry periods.
Ste. Genevieve Limestone (Mgl)
The Ste. Genevieve underlies rolling karst areas.
The limestone 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. The Ste.
Genevieve contains major caverns of the Mammoth Cave area, which have
large, connected, subsurface streams. 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)
The St. Louis underlies rolling karst areas. Its karst commonly has
less relief than karst on the Ste. Genevieve Limestone, but sinkholes
The St. Louis yields more than 50 gallons per minute to wells from large
solution openings in karst areas, but most other wells are inadequate
for a domestic supply with a power pump. It is a major spring horizon,
and many springs have low flows of several hundred to several thousand
gallons per minute. Many springs are used for public and industrial
Salem, Harrodsburg Limestones (Msh)
These rocks underlie gently rolling uplands and tops of some knobs,
and the Mississippian Escarpment (Muldraugh Hill) in Hardin, Larue,
southern Marion, and southwestern Nelson Counties. They form steep bluffs
above exposures of the Borden Formation.
These formations yield 100 to 500 gallons per day to drilled wells on
broad ridges or on uplands, and larger amounts when solution openings
are encountered close to perennial stream level. They also yield water
to springs at heads of ravines and on the face of the escarpment. 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
The Borden forms 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. Shale forms steep slopes, and the more resistant
siltstone beds form ledges on slopes and in ravines.
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 yields little
or no water to wells.
New Albany Shale (MDnb)
The New Albany forms broad, flat valleys with steep hillsides, and steep,
dissected bluffs along streams.
The New Albany yields 100 to 500 gallons per day to drilled wells in
broad valleys and on uplands, water to dug wells almost any place in
the black shale, and water to small springs that often go dry during
late summer and fall. Water is in fractures that extend less than 50
feet below the land surface. Water is hard and may contain salt or hydrogen
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 Hardin County are HA-33
to "Groundwater Resources in Kentucky"