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Alluvium (Qa)
Topography
The alluvium forms narrow flood plains 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 gal/min to most dug wells. Where sandy
material is present, and saturated thickness great enough, the alluvium
may yield more than 500 gal/day to screened drilled wells. Water is
soft or moderately hard; may contain large amounts of iron at depth.
Breathitt Group (Pbm, Pbl) (Princess Formation, Four Corners Formation,
Hyden Formation, Pikeville Formation)
Topography
The topography of the Breathitt is rugged; sandstone forms narrow valleys
and cliffs or steep slopes on hillsides and shale forms 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 gal/day to almost half of the wells
drilled in valley bottoms and less to wells on hillsides and hilltop.
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 is highly dissected 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
The Grundy yields 100 to 500 gal/day to wells in thick deposits. 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 semi-perched water
tables are common. Waters are soft too moderately hard, and sometimes
contain noticeable amounts of iron.
Paragon Formation (Mpn)
Topography
Hard beds of sandstones within this predominately shale formation forms
small cliffs or ledges.
Hydrology
Yields almost no water. Impermeable shale may hold water in overlying
sandstone and conglomerate.
Borden Formation (MDbb)
Topography
The Borden shale 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 gal/day to wells in valley bottoms, and
may yield more than 500 gal/day to drilled wells in broad valley bottoms
from fractured sandy rocks near streams. The Borden yields 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 to the construction of 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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