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Alluvium (Qa)
Topography
The alluvium forms extensive flood plains with small terraces along
Rolling Fork.
Hydrology
The alluvium yields 100 to more than 500 gal/day (gallons per day) from
thick deposits along Rolling Fork. Water is hard and may have a high
iron content.
Girkin Formation (Reelsville Limestone, Sample Sandstone, Bever
Bend and Paoli Limestone) (Mcl)
Topography
The Girkin forms the lower part of the Dripping Springs Escarpment.
The lower part of the Girkin underlies rolling karst areas near base
of escarpment, and contains numerous large sinks into which the overlying
sandstone has collapsed.
Hydrology
Most wells in upland areas are inadequate for domestic use, however
some wells yield enough water for a domestic supply (more than 500 gal/day)
from solution openings. Some wells produce more than 5 gal/min from
large solution openings. Near outcrop areas, particularly near major
escarpments, yields generally are inadequate during dry periods.
Ste. Genevieve Limestone (Mgl)
Topography
The Ste. Genevieve underlies rolling karst areas.
Hydrology
The Ste. Genevieve yields more than 50 gal/min 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 gal/min 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 Ste. Genevieve Limestone, but sinkholes are steeper.
Hydrology
The St. Louis yields more than 50 gal/min to wells from large solution
openings in karst areas. Most wells penetrate solution openings and
but may be inadequate for a domestic supply with a power pump. Major
spring horizon; many springs have low flows of several hundred to several
thousands of gallons per minute. Many springs are used for public and
industrial water supplies.
Salem, Harrodsburg Limestones (Msh)
Topography
These limestones underlie gently rolling uplands and tops of some knobs
and the Mississippian escarpment (Muldraugh Hill) in Larue County. They
forms steep bluffs above exposures of Borden Formation.
Hydrology
The limestones yield 100 to 500 gal/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 face of escarpment. Wells that encounter large
solution openings produce more than 5 gal/min. Water from wells is hard
but otherwise of good quality.
Borden Formation (Muldraugh (Mbf), Halls Gap, Nancy, New Providence
Members (MDbb))
Topography
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.
Hydrology
The Borden yields 100 to 500 gal/day to wells in valley bottoms, and
may yield more than 500 gal/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, common in this area. Most dug wells yield less
than 500 gal/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)
Topography
The New Albany forms broad, flat valleys with steep hillsides; steep,
dissected bluffs along streams.
Hydrology
The New Albany yields 100 to 500 gal/day to drilled wells in broad valleys
and on uplands. It yields water to dug wells almost any place in the
black shale. It also 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.
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.
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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