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Alluvium (Qa)
Topography
The alluvium forms narrow floodplains and underlies terraces. At least
one well-developed terrace is present along the principal streams of
the region.
Hydrology
The alluvium yields more than 100 gallons per day to most dug wells. Where sandy
material is present and saturated thickness great enough, the alluvium
may yield more than 500 gallons per day to screened drilled wells.
Breathitt Group (Pbl, Pbm) (Four Corners Formation, Hyden Formation,
Pikeville Formation)
Topography
The Breathitt Group underlies the valleys and forms the hills. Tops
of hills and ridges commonly are capped by sandstone. Shales form wide
valleys and moderate or gentle slopes on hills.
Hydrology
The Breathitt yields more than 500 gallons per day to almost half of the wells
drilled in valley bottoms and more than 100 gallons per day to about half the
wells drilled on hillsides and on ridges. Sandstones yield water to
most wells. Shales also yield water to many wells, and coal yields water
to a few. Near-vertical joints and openings along bedding planes yield
most of the water to wells. Waters are highly variable in chemical character.
Grundy, Alvy Creek Formations (contains Lee-type quartzose sandstones
of the former Lee Formation) (Plc, Plr)
Topography
Thick, resistant sandstones of the Grundy underlie an extensive upland
in McCreary County.
Hydrology
Generally, the Grundy yields more than 500 gallons per day to about
three-quarters of the wells drilled in valley bottoms and lowland areas
bordering streams and on hillsides. About half the wells on hilltops
yield more than 500 gallons per day. Deep wells that penetrate fractures
produce enough for a domestic supply and sometimes yield as much as
5 gallons per minute. Deep wells penetrating the entire thickness of
thick sandstone units in excess of 500 feet may yield enough water for
small municipal or industrial supplies. Sandstone is the principal aquifer,
but shale yields water to some wells and coal to a few. Joints and openings
along bedding planes, best developed in sandstones, supply most of the
water to wells. Waters are generally soft or moderately hard and contain
noticeable amounts of iron.
Paragon Formation (Mpk)
Topography
The Paragon forms moderate slopes beneath outcrops of massive sandstone
units of the Grundy Formation.
Hydrology
The Paragon yields little or no water to wells.
Bangor Limestone, Hartselle Formation, Kidder Limestone (Chesterian
Limestones) (Mpk)
Topography
The limestones form steep hillsides or underlie broad rolling karst
areas and dissected uplands.
Hydrology
The limestones yield 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)
Topography
The Ste. Genevieve underlies valleys.
Hydrology
Springs having low flows ranging from less than 10 gallons per minute
to more than 200 gallons per minute occur at or near stream level or
near the contact with the underlying St. Louis Limestone.
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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