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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 is great enough,
the alluvium yields more than 500 gallons per day to screened, drilled
wells. Water is soft or moderately hard, and may contain large amounts
of iron at depth.
High-level fluvial deposits (QTf)
Topography
These deposits lie in uplands and hilltops having no distinct surface
expression.
Hydrology
Wells in thick deposits yield 100 to 500 gallons per day. These deposits also
yield water to small springs.
Water is soft.
Breathitt Group (Pbm, Pbl) ( Four Corners Formation, Hyden Formation,
Pikeville
Formation)
Topography
The topography of the Breathitt is rugged, sandstone forming narrow
valleys and cliffs or steep
slopes on hillsides, and shale forming wide valleys and moderate or
gentle slopes on hills. Tops
of hills and ridges commonly are capped by sandstone.
Hydrology
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. The Breathitt 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
Thick, resistant sandstone in the Grundy forms an extensive upland in
western Wolfe County. The upland is highly dissected along its western
margin and northern part, and is characterized by steep-sided ridges
and cliffs 100 to 200 feet high. Waterfalls and rock bridges, such as
Natural Bridge and Sky Bridge, are common. Some cliff-forming sandstone
paleochannels have been cut through the Paragon Formation into limestone
units of Late Mississippian age.
Hydrology
Generally, the Grundy yields more the 500 gallons per day to most wells
drilled in valley bottoms. It yields more than 500 gallons per day to
about half of the wells on hilltops, and more than 500 gallons per day
to almost three-quarters of the wells on hillsides. It also yields water
to small springs. 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.
Borden Formation (MDbb)
Topography
Shale in the Borden forms dissected slopes, massive siltstone forms
cliffs, and limestone forms
ledges on shale slopes. The Borden forms broad, flat valleys.
Hydrology
The Borden yields 100 to 500 gallons per day to wells in valley bottoms.
It may yield more than 500 gallons per day to drilled wells in broad
valley bottoms from fractured sandy rocks near streams, but almost no
water to wells on hills. Water from wells drilled below stream level
may contain salt and sulfate less than 100 feet below the level of the
principal valley bottoms. Water from dug wells and small springs is
soft and has a low dissolved solids content. Because much of this formation
is soft and silty, it has been well suited for dug wells in the past.
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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