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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; 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, 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 plains yield
most of the water to wells. Waters are highly variable in chemical character.
May contain salty water 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 is highly dissected along its western margin
and 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. Inter-granular openings yield water to joints, and probably
directly to some wells. Perched and semi-perched 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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