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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
Where sandy material is present, and saturated thickness great enough,
the alluvium will yield more than 500 gallons per day to screened drilled
wells. Water is soft or moderately hard; it may contain large amounts
of iron at depth.
Breathitt Group (Pbu, Pbm, Pbl) (Princess Formation, Four Corners
Formation, Hyden Formation, Pikeville Formation)
Topography
The topography of the Breathitt Group is rugged; sandstones form narrow
valleys and cliffs or steep slopes on hillsides, and shales form wide
valleys and moderate or gentle slopes on hills. Tops of hills and ridges
commonly are capped by sandstone.
Hydrology
In the eastern half of Magoffin County, the Breathitt yields more than
500 gallons per day to most wells in valley bottoms and almost half
the wells on hillsides, and smaller quantities of water to wells on
hilltops. In the west-central part of Magoffin County, the Breathitt
yields more than 500 gallons per day to almost half of the wells drilled
in valley bottoms and less to wells on hillsides and hilltops. Sandstone
yields water to most wells. Shale also yields 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. Salty water may occur at depths less than 100
feet below the principal valley bottoms.
Grundy Formation (contains Lee-type sandstone of the former Lee
Formation) (Plc)
Topography
The upland of the Grundy Formation is highly dissected along its western
margin in the northern part of Magoffin County, and is characterized
by steep-sided ridges and cliffs 100 to 200 feet high. Some cliff-forming
sandstone paleochannels have been cut through the Paragon Formation
into limestone units of the Late Mississippian.
Hydrology
The Grundy yields more the 500 gallons per day to most of the wells
drilled in valley bottoms. It yields more than 500 gallons per day to
about half of the wells on hillsides and more than 500 gallons per day
to almost three-quarters of the wells on hilltops. Sandstone is the
principal aquifer, but shale yields water to some wells and coal to
a few. Vertical joints and openings along bedding planes, best developed
in sandstones, supply most of the water to wells. Intergranular openings
yield water to joints, and probably directly to some wells. Perched
and semiperched water tables are common. Waters are soft to moderately
hard, and sometimes contain noticeable amounts of iron.
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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